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Gear / Technical Help => Microphones & Setup => Topic started by: Gutbucket on September 18, 2019, 06:37:26 PM

Title: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 18, 2019, 06:37:26 PM
OMT Part 1 thread- http://taperssection.com/index.php?topic=96009.msg1279052#msg1279052 (http://taperssection.com/index.php?topic=96009.msg1279052#msg1279052)
OMT Part 2 thread- https://taperssection.com/index.php?topic=184876.msg2251211#msg2251211 (https://taperssection.com/index.php?topic=184876.msg2251211#msg2251211)

Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 18, 2019, 06:37:47 PM
--reserved--
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 18, 2019, 07:08:29 PM
I'm shifting a discussion here that started in another - ORTF + Central Omni thread at GS (https://taperssection.com/index.php?topic=191760.msg2309780#msg2309780) - then drifted into more oddball topics. 

It started getting into new OMT territory around the end of this post (https://taperssection.com/index.php?topic=191760.msg2311257#msg2311257), when we started discussing ideas about interference tube "shotgun" mics as Mid channel center mics.  The first part of that post was a rehash of conclusions I'd made concerning "ambient pair" mics over the course of the first two OMT threads.

then EmRR posted this oddball setup which sealed the deal!

(https://live.staticflickr.com/65535/48754825807_daac0049f0_z.jpg)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 18, 2019, 07:08:53 PM
When looking at your OMT pdf’s, I took it as a general approach to have the center somewhat forward of the spaced omni’s.  Trying to parse your thoughts above in that context.  I’m guessing some offset for minimal time of arrival, but not a lot?  I'm remembering 3-12" from somewhere. 

That's right. In my previous post in the ORTF + Central Omni thread thread I was referring to the common practice of positioning ambient mics significantly further back in the room than the main array - several meters or more.   Based on that I used to be concerned about how to achieve sufficient front/back spacing between main mics and ambient mics, but I'm no longer concerned with that and typically arrange things so the ambient/surround mics are only about 12" behind the others.

I do generally position the center microphone forward slightly.  That emulates other LCR microphone setups like OCT and Michael William's extension of Stereo Zoom to 3 or more channels, where doing that in specific combinations with L/R angle, spacing and pickup pattern is intended to provide "image linking" between the Left-Center and Center-Right sectors without excess image overlap or gap.  The ideal is that the "edge" of the imaging segment captured by the left/center stereo pair of channels should not extend over to the right side, but sort of seamlessly "hand-off"  the image to the center/right stereo pair of channels. This kind of thing may be more important for surround playback where it can achieve continuous image linking across speaker sectors, and where directional imaging can extend seamlessly beyond the L/R speakers out into the L-Ls and R-Rs sectors when things are setup correctly for it.  I can clearly hear this kind of smooth and solid image linking in surround playback when it's right.  Really cool and one of the reasons I keep my mic setups compatible with good surround playback even though I don't currently have any surround playback set up.

This is visually indicated in Image Assistant (https://schoeps.de/en/knowledge/image-assistant.html) when playing around with 3 mic L/C/R arrays, where it becomes evident that it takes some degree of center forward spacing to cause the imaging curves for the L/C and C/R sectors to line up correctly across the center. (Note: Image Assistant is a bit complicated and takes a bit of familiarization to be useful.  I prefered the old Java version which presented all the information on a single display instead of more modern "sparsely populated tabs".  The Sengpielaudio Visualiser (http://www.sengpielaudio.com/HejiaE.htm) is easier to understand making it a better resource for many, yet is limited to the visualisation of 2-channel stereo microphone setups)

But does that matter in a 2 channel stereo mix where those discrete imaging sectors are sort of being overlaid upon and woven against each other, and the center is a phantom position rather than a physical speaker corresponding to a discrete microphone channel defining the edge of each sector?  It's certainly not obvious in the same way when listening back as there is only one Left-Right sector between the two speakers (not counting the non-imaging "beyond the speakers" region of diffuse sound).  My feeling is it's less likely to matter, partly because of that but also because I'm typically manipulating the level of channel pairs against each other more in a 2ch mix to sort of layer them, and as channel gains are changed relative to each other, the image linking relationships shift.  In surround I'm balancing pairs and  the level of sectors against each other, but the separate sectors are intended to be "contiguous" rather than "overlaid".

I'll note that for practical reasons, sometimes over the past year or so I've ended up angling the telescopic arms which support the omnis and L/R supercards slightly forward, causing the center to no longer be forward of those mics.  Usually that's done to squeeze the array into an odd spot, or as a way to angle the L/R facing mics more forward when necessary.  Since I'm not currently set up for surround playback set up I've not listened to these particular recordings in surround mode to determine how much impact that lack of forward-spacing on the center mic has on image linking across segments.   Doesn't seem to pose any problem in the 2-ch mix.

In any case, I don't think forward spacing of the center in relation to the omnis is a major factor.  It's more important in keeping an appropriate geometric relationship between the center any near-spaced mic positions adjacent to it. In my case the side-facing L/R and rear-facing Ls/Rs supercards, and in simpler OMT setups the similar spacing between the single front-facing and back-facing mics. 

Quote
Within MS, as I said previously, I've liked the addition of a pressure omni for the lows, and that could be high passed.  I'm curious whether that will at all prove useful with spaced omni's, I'm thinking maybe not. 
 

The addition of a single pressure omni coincident with a M/S rig changes things in less complex ways than the addition of a center single omni to ORTF.  Essentially, beyond extending sensitivity to lower frequencies, it shifts the Mid channel pickup pattern more toward omni.  With all 3 mics coincident in space, there isn't the complex 3-way phase relationship ORTF + a center omni produces by occupying 3 non-coincident near-spaced positions.

Quote from: EmRR
Quote from: Gutbucket
Likewise I'm currently curious how a true shotgun (albeit a short one) as Mid compares against the supercard Mids I'm using

I will get back to this question.  I’ve run the KMR 81i twice, once in MS and once with two in a PAS array along with a MS pair and a board feed.  The PAS was kinda weird in the imaging, as dsatz has frequently pointed out.  It does have that certain Neumann lower midrange quality we like so much.  In both cases, the highs are both clear (on-axis) AND muffled (off-axis), I can hear the interference tube for better or worse.  I take his point that the off-axis stuff will have a much smoother transition with a supercard in the upper mids and highs, and in the lower registers sound mostly the same.   With the MS version I have a full multitrack to combine it with, the PAS version worked OK as supplemental 'focus' fill with the MS doing most of the work, plus I like that particular mic's low mid contribution. 

This is a good discussion.  My hope is that the audibly bad off-axis behavior of an the interference-tube center microphone will be low enough in level to be masked by the contribution of the other microphones in the array.  The other microphones are on-axis covering the center-mic's off-axis directions and they have good off-axis behavior themselves.  If that making effect holds true, the additional forward-axis clarity from the higher directivity of a gun-mic should make it beneficial over a less tightly focused supercard with superior off-axis behavior in the special center position.  Of course it also depends on how heavily one needs to lean on the center channel in the mix - off-axis interference-tube artifacts will be boosted by the same amount as the good on-axis signal as center channel level is increased.  That kind of mix decision is subjective, and is honestly one of the more important mix variables. Sometimes center channel needs to be boosted significantly to achieve sufficient clarity and psychoacoustic proximity.  Doing so intentionally biases the array more strongly toward the forward-axis.  The ability to do that can really benefit the recording when that's needed, even if it collapses the soundstage width somewhat (and may compromise sector image linking in surround), and is not a true representation of how it would have sounded to a listener standing at the recording location. < But I don't care at all about that kind of documentary recording anyway.  I want to make the best sounding recording I can which convinces the listener of its "realness" by how good it sounds.  Working the illusion.

Quote
I feel like I'd use the shotgun MS setup in a pinch in a big distant room again, if I knew I wouldn't have much footprint or options, I don't see myself revisiting a close spaced pair again anytime soon, maybe widely spaced in a larger multitrack situation.

I've thought about a pair of shotguns versus a single one as Mid or as the C in L/C/R.  I do think a PAS pair could be useful, however I'd set them up as a coincident pair rather than near-spaced and tweak stereo width afterward.  I would do so partly as the logical final step towards increasing PAS directivity for good clarity (each gun on axis with a stack, rather than one centered between stacks) and partly to optimize pickup of whatever stereo information is present in the PA mix, assuming there is any.  Upon reflection, these are actually two sides of the same coin.   Stereo width adjustment of the pair in post manipulates the sum and difference information between the two channels. By increasing stereo width (increasing the ratio of Side vs Mid) we are emphasizing the difference between those channels.  And if that difference is more or less solely determined by the difference in source content each is on-axis with, rather than time-of-arrival phase-differences at LF extending to phase-randomization at HF from the non-coincident near-spacing, it would seem such a width adjustment would better target just the differences in direct sound between the two sides of the PA, in comparison with a single forward facing gun + stereoization of it with a bi-directional oriented 90 degrees off-axis.   Essentially, this is a special-case of the old comparison of the virtues of X/Y verses M/S coincident stereo and the advantage one may have over the other when both can be setup with one goal in mind then ratio adjusted in post to best effect with another goal in mind.  Hope that makes sense.

I don't really want to run X/Y shotguns (to awkward and bulky), and have no shotguns anyway so I probably will never get around to trying this.  But I would have loved to have tried taping Dan Healy's lush stereo Dead mixes this way in combination with a pair of wide omnis, as sort of the inverse of the then common to that era technique of a near-spaced shotgun pair + single omni. 

Quote
I gotta wonder if there is value in using only one, pointed directly at the closest stack rather than at the center of the stage, then mixing it in the center of another stereo array.  It's usually vocal register stuff I'm missing, and dead on the stage adds more drums than anything, which is NOT the deficit in the other arrays.

Yes you can!   I've done something very similar when taping non PA amplified acts up close, to specifically focus on something I wish to highlight and dominate the center of the playback image.  For instance I'll point the center mic at the snare or more toward the primary player to increase pickup of that source (the center mic gets angled more toward one side), even though the rest of the mic array may be angled somewhat differently to get even Left/Right pickup of the entire band and a correct front/back relationship between band and audience. This can be quite useful up close.  For PA taping, if close enough to the PA that there is significant differentiation between pointing a center shotgun at a stack (more vocals) versus the between the stacks (more drums) it should work the same.  In that way, the center microphone can be thought of more as a primary emphasis thing rather than a hard direction with respect to the other mic channels when recording.  Likewise its level (and EQ) control emphasis of proximity and clarity in the mix.  It is only its panning in the mix where perceived direction comes into play. In the stereo mix you can pan the center microphone slightly to one side or the other of center to balance things as necessary.  This aspect is really cool and one of the really useful flexibility in mixing things.   
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on September 18, 2019, 07:32:48 PM
My hope is that the audibly bad off-axis behavior of an interference-tube center microphone will be low enough in level to be masked by the contribution of the other microphones in the array.  The other microphones are on-axis covering the center-mic's off-axis directions and they have good off-axis behavior themselves.  If that masking effect holds true, the additional forward-axis clarity from the higher directivity of a gun-mic should make it beneficial over a less tightly focused supercard with superior off-axis behavior in the special center position. 

I'd say that seems totally true.  In the context of the shotgun alone as Mid of a MS array with minimal side contribution to the mix, I'm hearing the interference tube.  Not necessarily bad, just a different quality, less seamless image from center to sides. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: rocksuitcase on September 18, 2019, 10:35:22 PM
As Lee knows we have tried the AKG ck8 as a center mic a few times over the years since we first tried OMT (2016 January was the first OMT for us) Then Greyfox 2016 we slammed a bunch of OMT and have been trying it ever since. Recently, at Adirondack Independent Music Festival, I ran the ck8 all day for five sets including Twiddle, Ryan Montbleau, and Kung Fu, all on the LMA. My reasoning was expecting a loud Rock n Roll PA, anticipating chatty crowd at outdoor all day festival, therefore might utilize the rejection from the ck8 shotgun pattern. I need to write up more of our OMT3, 4 and 6 experiments for this thread, and hope to have time soon. Meantime,here are a few pics of the ck8 as a center and a few links. (gakbrellas rock!)

https://archive.org/details/Twiddle2019-08-31.akgomt           
https://archive.org/details/kungfu2019-08-31.akgomt-24
https://archive.org/details/ryanmntblu2019-08-31.akgomt-24

https://archive.org/details/delmccoury2016-07-15.24.ck22ck8ck61

pic 1: AKG ck22 x 2 spread 90cm| AKGCK8 fwd 0'|AKGck61 rear 180'
pic 2 & 3: AKG ck22 x 2 spread 90cm| AKGCK8 fwd 0'|AKGck61 rear 180'|AKGck61 fwd 0'|AKGc414 XLSII x 2   [2 separate rigs- the 414's were stereo pair, the ck8 and ck61 aimed forward in the OMT4 using 5 mics (neat eh?) was for comparison]. I wound up mixing the ck8 and not the 61 for all the sets.

 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on September 18, 2019, 11:46:26 PM
As Lee knows we have tried the AKG ck8 as a center mic a few times over the years since we first tried OMT (2016 January was the first OMT for us) Then Greyfox 2016 we slammed a bunch of OMT and have been trying it ever since. Recently, at Adirondack Independent Music Festival, I ran the ck8 all day for five sets including Twiddle, Ryan Montbleau, and Kung Fu, all on the LMA. My reasoning was expecting a loud Rock n Roll PA, anticipating chatty crowd at outdoor all day festival, therefore might utilize the rejection from the ck8 shotgun pattern.

Yeah, that works! 

I was just in Albany week before last for my wife's family reunion, went up above Lake George and hiked Cat and Thomas.  Seems like there's a lot of cool music going on there.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on September 19, 2019, 09:39:17 AM
Sanken double MS teaser video:

https://vimeo.com/360264311
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 19, 2019, 11:19:32 AM
^ Interesting. 

I'm seriously considering picking up a short stereo shotgun with M/S output if I can find a decent one for a reasonable price.  Having the Side channel built in will keep the rig as compact as possible and simplify mounting, wind screening, and cabling. Sanken CMS-50 is one candidate.  The WMS-50 linked above looks like they took the CMS-50 and added a rear-facing capsule and a second output connector.  That raises the question of how much spacing is desirable between the forward facing and rear-facing ambient/audience channels.  In the WMS-50 design, as in any DMS setup, there is no spacing of significance.  That's necessary for DMS using a single Side channel, and is how the microphone is kept small and compact to make it appropriate for video and film use on camera or on boom where a single microphone providing a 4 or 5 channel output can be mounted inside a blimp.

I'd be really happy to find a coincident arrangement of front and rear facing mics ideal for OMT.  That WMS-50 plus spaced omnis would make for an OMT6 rig using only 3 microphones.  Same with an ambisonic mic in the middle.  But I doubt it will be.   I think what is optimal is coincident stereo across the front, near-spaced multichannel stereo bolstering that with directional cues from all other directions and knitting everything together, and wide-spaced omnis providing decorrelated diffuse ambient pickup and bass heft.  By comparison I consider coincident-stereo all the way around make be a significant compromise in spatial quality, but it is very attractive in terms of practicality.

It is interesting comparing the newly announced WMS-50 above to the WMS-5 model it replaces.  The modifications seem to be raw Double Mid/Side output on two seperate mini XLRs (front M/S + rear M/S) rather than de-matrixed 5.0 L/R/C/Ls/Rs output on a single multi-pin fullsize XLR.

My reasoning was expecting a loud Rock n Roll PA, anticipating chatty crowd at outdoor all day festival, therefore might utilize the rejection from the ck8 shotgun pattern. I need to write up more of our OMT3, 4 and 6 experiments for this thread, and hope to have time soon.

Yep, that's the idea behind using a shotgun-mic in the center.  Looking forward to reading more about your thoughts on the variations you've tried.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: rocksuitcase on September 19, 2019, 11:57:12 AM
I think you should try this double MS style or stereo shotgun for what you are doing. Sure makes sense. We have used the c426 only 2-3 times as the front/rear coincident. the result sure is smooooth!. Makes for easy mixing and editing etc.
Just for grins, how much is that Sanken WMS50?     ;D

Here is fuzzy snap using the c426 as the coincident center. We also ran akgck22 spread 4 feet, AKGck3 50' angle, a bit inside of PAS.  so the mix was an OMT 6 on the Dr680 and kindms did not run a deck.

Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 19, 2019, 12:52:54 PM
That's why I want to get the Tetramic operational again even though it won't provide a shotgun center.  It will otherwise will make for a good test of D-M/S /ambisonics in the center between wide omnis and serve as a compact second rig assembled from gear I already own.

No pricing on (D-M/S) WMS-50 yet.  Found a listings for WMS-5 (the model it replaces) at B&H and Full Compass @ $4,750 which is far too rich for my use. 

Full Compass has the (M/S) CMS-50 listed @ $895 which is within reason, yet that's about half the $1750 price quoted elsewhere so could be a mistake.  Unfortunately I just discovered that it uses a cardioid Mid capsule behind its short tube though, where I would prefer a tighter supercard like the (mono) CS-M1 http://www.sanken-mic.com/en/product/freqpola.cfm/8.1001900 (http://www.sanken-mic.com/en/product/freqpola.cfm/8.1001900).  In the frequency response graph on that page you can see it's better off-axis rejection through the full range (especially at HFs) in comparison to CMS-50 http://www.sanken-mic.com/en/product/freqpola.cfm/8.1002000 (http://www.sanken-mic.com/en/product/freqpola.cfm/8.1002000).

Unfortunately, B9Audio's post today in the B9Audio thread doesn't convey strong enthusiasm concerning my proposal for them to produce a modular M/S stereo microphone with a fixed S capsule and amplifier body which would accept interchangeable Mid capsules of various pattern (any B9 capsule, currently including: omni, subcard, widecard, cardioid, supercard, and a short shotgun), or a blank end-cap for straight fig-8 use.  That suggestion is rooted in my thinking about all this, but I think this kind of modular stereo mic could make for a popular product well beyond the taper micro-niche.  It would be unique amongst its competition and serve to differentiate B9A as not just a producer of Schoeps clones, but as innovator.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on September 19, 2019, 01:09:31 PM
raises the question of how much spacing is desirable between the forward facing and rear-facing ambient/audience channels.  In the WMS-50 design, as in any DMS setup, there is no spacing of significance. 

I'd be really happy to find a coincident arrangement of front and rear facing mics ideal for OMT.  That WMS-50 plus spaced omnis would make for an OMT6 rig using only 3 microphones.  Same with an ambisonic mic in the middle.  But I doubt it will be.   I think what is optimal is coincident stereo across the front, near-spaced multichannel stereo bolstering that with directional cues from all other directions and knitting everything together, and wide-spaced omnis providing decorrelated diffuse ambient pickup and bass heft.  By comparison I consider coincident-stereo all the way around make be a significant compromise in spatial quality, but it is very attractive in terms of practicality.

I really wonder where the sweet spot is.  An all in one mic that does everything may be just as expensive as having all the discrete tools, and constrain your placement options. 

Since more often than not I'm doing this in an official capacity for a band, I may be slightly less pressed for rig compactness, but I still feel that pressure, also from a safety and liability point.  Even working 'officially', so many things in smaller venues are pure 'seat o' the pants' in approach. 

Since I've got a pair of MKH 30, I'd be inclined to add a forward/back bar and just run two center MS pairs separated by some space.....and it's another thing for me to try sometime. 

Right now I'm still going through the options with the dual output mic, focusing on the variable mid pattern in post thing.    I might consider front center with the dual output mic for pattern variability, also with the shotgun stacked in there (either aimed center coincident or PAS coincident, depending on the situation....argh, another custom swivel mount). Rear cardioid MS spaced near coincident to the front MS (don't own a dedicated supercard)....hmmm...what spacing?  AB omni to the sides. 

All that raises the question of delay use, and what it might or might not do for you.  Duplicate a set of DMS output channels and delay one set to simulate spacing.  Not the same result as the real thing, but maybe also useful, lacking the real thing.   In studio work I have delayed the rear output on certain room sounds to create artificially long first reflections, or used the delayed signal to feed reverbs, not using the delayed signal in a raw audible form. 

That new Sanken (timing and price unknown) looks like it would still let you derive all the various dual diaphragm center patterns through a different work path, if you duplicated signals in post and took the rear MS down to mono, killing the S contribution.  You could derive supercard mids with a bit of work in post.  Seems as compact as a Tetramic.  But ouch that's expensive. 

Working mostly in controlled small studio settings, I have always gravitated to coincident spacing, and it's interesting to think through the 'why's'.  I tend to work with live bands in studio, so there's a lot of non-coincident bleed between multiple mic sources already. Perhaps coincident placement in that context gives some counterbalance to the bleed. 

Someone really needs to grab my Oktava Figure Eight in the Yard Sale before I find another way to incorporate it!  : )
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 19, 2019, 01:12:07 PM
Note to EmRR..

This morning I edited the post I made here yesterday, adding the paragraph below as another angle-about/justification-for some forward spacing of the center microphone:

This is visually indicated in Image Assistant when playing around with 3 mic L/C/R arrays, where it becomes evident that it takes some degree of center forward spacing to cause the imaging curves for the L/C and C/R sectors to line up correctly across the center. (Note: Image Assistant is a bit complicated and takes a bit of familiarization to be useful.  I prefered the old Java version which presented all the information on a single display instead of more modern "sparsely populated tabs".  The Sengpielaudio Visualiser is easier to understand making it a better resource for many, yet is limited to the visualisation of 2-channel stereo microphone setups)

..it also ties the coincident DMS question to the forward spacing of the center mic thing, and gets to another reason I suspect near-spacing all directional mics except for the center forward-facing position is likely to be superior, if less practical, assuming gear of equal quality is used.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on September 19, 2019, 01:17:15 PM
^
cool, thanks.  I haven't checked out that part of Image Assistant. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on September 19, 2019, 04:11:29 PM
Lauten LS-308 could figure into this conversation.  I don't know anyone that's used one yet.  Second order cardioid with two capsules.   It'd be a pain to mount in an array. 


(https://i.imgur.com/wHKRfnb.jpg)

https://www.youtube.com/watch?v=wSAoaxHND28 (https://www.youtube.com/watch?v=wSAoaxHND28)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 19, 2019, 04:34:17 PM
Since I've got a pair of MKH 30, I'd be inclined to add a forward/back bar and just run two center MS pairs separated by some space.....and it's another thing for me to try sometime. 

I did that a few years ago for a few sets at the Wanee festival but still have not gotten around to messing with that part of the recordings.  I was running my then-standard OMT6 setup using single front/back near-spaced supercards in the center + OCT L/R supercards + wide omnis, and figured I'd add the two Naiant fig-8s I had so they were coincident with the front/back facing supercards.  I managed that by running the two fig-8 side-channels into a V3 and used it's SPDIF out to record that onto the stereo channel of the DR-680 without otherwise altering the rest of the setup.  Photos and comments are posted somewhere in the OMT pt2 thread in the Pt1 thread. (http://taperssection.com/index.php?topic=96009.msg2181501#msg2181501)

(http://taperssection.com/index.php?action=dlattach;topic=96009.0;attach=121515;image)

(http://taperssection.com/index.php?action=dlattach;topic=96009.0;attach=121521;image)

(http://taperssection.com/index.php?action=dlattach;topic=96009.0;attach=121523;image)

I remember thinking about which way I should orient the positive lobe of the Side fig-8 for the rear-facing M/S pair, and I think I settled on both 8's having their positive lobe facing left (stage right).  I'd have to check my notes to be sure.  Obviously one can invert polarity to flip it either way, but this orientation seemed less confusing.  Also its in agreeance with how the rear-facing part of a standard Double M/S setup is handled, except for using separate Side mics instead of sharing a single one.

Quote
All that raises the question of delay use, and what it might or might not do for you.  Duplicate a set of DMS output channels and delay one set to simulate spacing.  Not the same result as the real thing, but maybe also useful, lacking the real thing.   In studio work I have delayed the rear output on certain room sounds to create artificially long first reflections, or used the delayed signal to feed reverbs, not using the delayed signal in a raw audible form.

Delay is certainly an option to play around with and can be useful.  When using the omnis as surround channels I found that in order to be able to use the most appropriate level of that content I sometimes need to apply a touch of delay to perceptually keep the front image locked in front rather than leaking too much into the surrounds.  It works to serve that purpose.  Yet I'd rather set things up so I don't need to do that, because to the same degree that it improves front/back separation for sounds arriving from the front, it compromises the admittedly much less critical directional imaging from all directions other than the front.  For example, with such a delay in place, distinct sounds which should be heard originating behind the listener or off to the side are reproduced first in front (to the extent that the content bleeds into the front microphones) before the delayed surrounds reproduce the direct arrival which actually reached their microphones first.   

That's why I speculated a few years back about substituting rear-facing subcardioids for the wide-spaced omnis when I was using the omnis to feed the surround channels- the idea being that as almost-omnis they would still capture good LF extension, yet their directional pattern would attenuate the mid and high frequency directional content arriving from the front by -6dB (the difference in subcard rear vs front sensitivity) without that content being overly colored due to the good off-axis behavior of subcards.  That's attractive because I'd noted an approximate 6dB difference between the the prefered level for the surround channels and the maximum level at which the front image stayed locked in front without delay applied to the surround channels.   The ephemeral small/lightweight AT853 subcards may have worked really well for this, but owning no subcards myself instead I reinstituted use of the DIY spherical APE balls to make the 4061 omnis a bit directional if only at HF, oriented to face backwards +/- 45 degrees.  Probably still needs delay or EQ to avoid the front image pull to the rear, but maybe a bit less of it.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 19, 2019, 05:17:48 PM
Lauten LS-308 could figure into this conversation.  I don't know anyone that's used one yet.  Second order cardioid with two capsules.   It'd be a pain to mount in an array. 

Interesting, hadn't seen that yet.  Here's their webpage on that 2nd order cardioid- https://www.lautenaudio.com/ls-308

Looking for photos with enough light through its elongated screen housing basket to reveal what's in there, it seems like it uses a more-or-less-standard double-sided capsule positioned at the silver end of the basket.  See this photo which seems to show empty space in the black portion of the basket- 

(https://static.wixstatic.com/media/7e594b_633774c703f840379241d6e4c937880e~mv2.jpg/v1/fill/w_326,h_277,al_c,q_80,usm_0.66_1.00_0.01/ls308%20tom%20toms%20back%20left.webp)

Presumably it uses some kind of interesting fixed filtering rather than a straight sum/difference electrical summing network like an electrically switched multipattern LD does using a similar double-sided capsule.  Perhaps the elongated basket is to keep the region immediately behind the mic clear enough for the fancy filtered summing to work correctly without unwanted rear-proximity artifacts.   /speculation

Precedent is the Schoeps SuperCMIT which incorporates a separate rear facing supercardioid in the same mic body along with advanced DSP processing to increase off-axis rejection in their fancy digital output only shotgun.  When you brought the Sanken WMS-50 to my attention this morning I noted its rear-facing capsule, and thought - "this thing could potentially have DSP processing applied similar to what the SuperCMIT is doing in order to increase off-axis rejection performance of the forward facing shotgun, applied afterward in post".  Granted the SuperCMIT filtering is proprietary and presumably needs to be custom tuned to the particulars of the microphone to work correctly.

I suspect we are likely to seem more of this kind of directional enhancement using multiple capsules in one microphone + clever signal processing in the future.. and not just in >1st order ambisonic mics where it is now mostly found.  I can imagine a microphone similar to the WMS-50 which leverages all its capsules in order to improve directionality and off-axis performance along all axes to an extent otherwise not possible from the raw output of each capsule alone.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on September 20, 2019, 12:11:26 PM
Since I've got a pair of MKH 30, I'd be inclined to add a forward/back bar and just run two center MS pairs separated by some space.....and it's another thing for me to try sometime. 

I did that a few years ago for a few sets at the Wanee festival but still have not gotten around to messing with that part of the recordings.  I was running my then-standard OMT6 setup using single front/back near-spaced supercards in the center + OCT L/R supercards + wide omnis, and figured I'd add the two Naiant fig-8s I had so they were coincident with the front/back facing supercards. 

Super compact!

Quote
All that raises the question of delay use, and what it might or might not do for you.  Duplicate a set of DMS output channels and delay one set to simulate spacing.  Not the same result as the real thing, but maybe also useful, lacking the real thing.   

Delay is certainly an option to play around with and can be useful.  When using the omnis as surround channels I found that in order to be able to use the most appropriate level of that content I sometimes need to apply a touch of delay to perceptually keep the front image locked in front rather than leaking too much into the surrounds.  It works to serve that purpose.  Yet I'd rather set things up so I don't need to do that, because to the same degree that it improves front/back separation for sounds arriving from the front, it compromises the admittedly much less critical directional imaging from all directions other than the front.  For example, with such a delay in place, distinct sounds which should be heard originating behind the listener or off to the side are reproduced first in front (to the extent that the content bleeds into the front microphones) before the delayed surrounds reproduce the direct arrival which actually reached their microphones first.   


The timing displacement of delay in this range doesn't seem like it would exceed 1-2 mS normally.  In most cases it seems to present as a barely detectable stretching of the room.   I need to play with it more.  I feel like the bigger difference I hear is whether or not there are multiple triangulated timing differences, or an artificial triangulation. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on September 20, 2019, 03:46:04 PM
I think what is optimal is coincident stereo across the front, near-spaced multichannel stereo bolstering that with directional cues from all other directions and knitting everything together, and wide-spaced omnis providing decorrelated diffuse ambient pickup and bass heft.  By comparison I consider coincident-stereo all the way around make be a significant compromise in spatial quality, but it is very attractive in terms of practicality.

Not gonna argue with that at all, but:

One thing I've noticed with the Sennheiser MKH mics in MS or DMS is improved spatial quality and much deeper bass.  They are the first mics I've owned that rendered an image which made me have vivid flashbacks to the space during the capture.  The recording I ran the other night has more bass in the MS than it does in the spaced Oktava omni's, which deliver the bottom almost too well on their own.  If I go to omni mid with the MKH 800 Twin, it's almost too much.  If I were to guess what those mics improve upon, it's greater linearity in response at all angles.  Not that the spaced omni's don't add spatial quality, they certainly do, just that there is probably always room for improvement within what's used in coincident positions.  Those mics were a huge stretch for me, and I've felt justified in the decision every time I hear the results. 

I'm at a loss to evaluate surround mixes, which I'm sure would change my perspective a lot.  I can generate them easily, there's just not a monitor system in place to give guidance.   
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kindms on September 20, 2019, 05:11:51 PM
we rant a pseudo OMT last night

split dpas, akg ck61 PAS and AKG c426 hyper x/y 90deg

rsc taped the dpas to the railing

Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 20, 2019, 06:23:57 PM
^ Right on.  I need to go tape something!

RE: two center MS pairs separated by some space

The timing displacement of delay in this range doesn't seem like it would exceed 1-2 ms normally.  In most cases it seems to present as a barely detectable stretching of the room.   I need to play with it more.  I feel like the bigger difference I hear is whether or not there are multiple triangulated timing differences, or an artificial triangulation. 

The typical delay needed to help disassociate the front image from bleeding into the surround channels is in the 10-25ms range, or an order of magnitude more than the 1-2ms corresponding to the front/back microphone position spacing.  Still not long enough to be perceived as a discrete echo or reflection but easily audible, but shifts directional imaging around strongly. 

I've played around with shorter 1-4ms time difference compensations for the center channel using both a physical center speaker and a phantom center.  It makes an audible difference yet is considerably more subtle.  I'm not convinced a precise alignment is critical..  or rather, I've convinced myself that I needn't worry too much about exact center mic spacing forward, partly because I can tweak center timing a bit withing that range if it helps lock in the front image or transient clarity.

Delay and level compensation is something Image Assistant lets you model as well, although that's hidden in a separate preferences popup.  Without adjusting any of that, Image Assistant assumes equal level and timing across all microphone channels.  Some of William's multichannel microphone array setups specify time and delay compensations to be applied to certain channels for the image linking between sectors to line-up correctly.  A smaller subset of them are "native arrays" which work as intended without any such compensation.  I find his arrays work well in terms of natural imaging, but I'm not concerned with achieving super accurate image-linking all the way around the listener including the side and back sectors so I tend to use his setups more as "known good" guidelines.  When I'm thinking about the multichannel microphone setup geometry I want, I'll search through his setups and compare a few which are close to what I want for other reasons, sort of converging on a solution.

One thing I've noticed with the Sennheiser MKH mics in MS or DMS is improved spatial quality and much deeper bass.  They are the first mics I've owned that rendered an image which made me have vivid flashbacks to the space during the capture.  The recording I ran the other night has more bass in the MS than it does in the spaced Oktava omni's, which deliver the bottom almost too well on their own.  If I go to omni mid with the MKH 800 Twin, it's almost too much.  If I were to guess what those mics improve upon, it's greater linearity in response at all angles.  Not that the spaced omni's don't add spatial quality, they certainly do, just that there is probably always room for improvement within what's used in coincident positions.  Those mics were a huge stretch for me, and I've felt justified in the decision every time I hear the results.

I've never used them but those Senns are hard to beat in those aspects from everything I've heard from folks like yourself familiar with them.  I suspect it's their linearity of response at all angles combined with good phase behavior throughout the frequency spectrum and phase match between microphones.  Those kind of attributes should be important for a coincident technique work at its best.  By contrast spaced omnis are essentially randomizing phase above a certain frequency as determined by the spacing between them, goodness almost in sort of a diametrically opposed way.

A really good coincident stereo recording can stand so well on its own in depth and spatial terms that it sometimes causes me to question the stereotypical conceptions of coincident verses spaced stereo techniques.  I think the quality of the microphone(s) has a lot to do with that.  And I think its also dependent on a good recording situation.  It doesn't fake things so much, even in a good way, but rather gets things right or not right within the ultimate constraint of how good the soundfield situation was in the location where the microphones were placed. 

Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on September 20, 2019, 06:32:09 PM

RE: two center MS pairs separated by some space

The timing displacement of delay in this range doesn't seem like it would exceed 1-2 ms normally.  In most cases it seems to present as a barely detectable stretching of the room.   I need to play with it more.  I feel like the bigger difference I hear is whether or not there are multiple triangulated timing differences, or an artificial triangulation. 

The typical delay needed to help disassociate the front image from bleeding into the surround channels is in the 10-25ms range, or an order of magnitude more than the 1-2ms corresponding to the front/back microphone position spacing.  Still not long enough to be perceived as a discrete echo or reflection but easily audible, but shifts directional imaging around strongly. 

I've played around with shorter 1-4ms time difference compensations for the center channel using both a physical center speaker and a phantom center.  It makes an audible difference yet is considerably more subtle.  I'm not convinced a precise alignment is critical..  or rather, I've convinced myself that I needn't worry too much about exact center mic spacing forward, partly because I can tweak center timing a bit within that range if it helps lock in the front image or transient clarity.

10-25mS; ok, totally different ballgame.  What about with a stereo mix?  That's where my thinking was.   
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 20, 2019, 07:12:37 PM
I haven't messed with center channel timing tweaks in stereo mixes as much.  In some ways it might matter more than with discrete L/C/R playback because in the 2ch case its summing electrically in the mix rather than "in air" in the room, which could make for more audible combing related effect.  Let me know what you find if you play around with it.  I'll do the same.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on September 21, 2019, 12:25:24 PM
I wonder what spacing standards exist, or if there are opposing schools of thought, amongst nature recordists.  Im thinking particularly of the low end from lightning strikes.   Might put some outside fenceposts on the concept, or it might not.....maybe just another signpost. 

I duplicated the rear signal from the MKH 800 Twin and delayed it a bunch of different ways, in a mix with the front and rear also combined to make a wide cardioid as part of a MS signal.  I didn't find anything with that particular situation that sounded better, always a more cloudy result when I really started comparing mute/unmute.  Probably more of a surround thing. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 23, 2019, 09:32:45 AM
I suspect so.  Thanks for the confirm on delays to coincident channels in the stereo mix. 

Interesting angle on nature recordists' approach for low frequency capture.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on September 24, 2019, 09:46:42 AM
Interesting angle on nature recordists' approach for low frequency capture.

I've done a good bit of thunderstorm captures with omni MS, and you get good crackling motion, but main strike is always close to mono.  I wonder what decorelation does for that, or if it's impractical due to the very low frequency.  It may blur the directional cues in the coincident image by the time it's wide enough to give effect.  Or it may require severe low-passing. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on September 28, 2019, 06:16:26 PM
Grabbed an Impact LS-3SAP pole, seems unique in that it has a 2 way socket that'll give you a right angle, or remove the stud to used it as an extension.  I haven't noticed any other mention of this hardware around here. 

https://www.bhphotovideo.com/c/product/1339819-REG/impact_ls_3sap_adjustable_pole_with_socket.html

I used the right angle socket to mount it to a Manfrotto 154 as a width extension, and with the Manfrotto pole moved all the way to one side, you can get 2 feet out on either side of center, more if not worried about center.  V shaped bars are easy too, if you wanted to have center forward of sides. 

https://www.bhphotovideo.com/c/product/503258-REG/Manfrotto_154B_154_Triple_Microphone_Holder.html/c/product/503258-REG/154_Triple_Microphone_Holder_Bar_Black_
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: prepschoolalumniblues on September 29, 2019, 02:25:47 AM
I did some searching bu couldn’t find much... had anybody tried using a figure-eight mic as a center channel between two split omnis? I feel like I might be misunderstanding how that type of microphone works... but it seems like if you had a MixPre-3 this setup would give you both the center clarity from the stage and some of that rear-facing goodness that OMT advocates.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on September 29, 2019, 07:48:16 AM
I did some searching bu couldn’t find much... had anybody tried using a figure-eight mic as a center channel between two split omnis? I feel like I might be misunderstanding how that type of microphone works... but it seems like if you had a MixPre-3 this setup would give you both the center clarity from the stage and some of that rear-facing goodness that OMT advocates.

I have landed on figure 8 center sometimes, gives the most forward directional pattern (outside of a shotgun, which will be more forward in the upper mids and treble, but less forward in the lows), fine so long as having the rear pattern is cool.  If there's a bunch of junk from behind then it won't be so great.  Rejects maximum up/down/side, can be good in narrow rooms or low ceilings.  If PA is wide relative to stage, then you might miss some PA sound with figure 8.  All depends on position. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 30, 2019, 11:05:22 AM
Grabbed an Impact LS-3SAP pole, seems unique in that it has a 2 way socket that'll give you a right angle, or remove the stud to used it as an extension.  I haven't noticed any other mention of this hardware around here. 

https://www.bhphotovideo.com/c/product/1339819-REG/impact_ls_3sap_adjustable_pole_with_socket.html (https://www.bhphotovideo.com/c/product/1339819-REG/impact_ls_3sap_adjustable_pole_with_socket.html)

That's the most recent one I picked up a while back.  Works well into a superclamp because it allows me to orient the extension either vertically or horizontally from the clamp. I most frequently use it in combination with one of these folding feet to create a short stand:

https://www.bhphotovideo.com/c/product/1119713-REG/impact_ls_3sb_backlight_stand_base.html (https://www.bhphotovideo.com/c/product/1119713-REG/impact_ls_3sb_backlight_stand_base.html)

A few weeks ago I played around with finding the best way to record a friends jazz trio at their regular outside patio gig.  No PA, and no real good place to put the rig without it being either overly distant or in the way directly in front of the band, so I tried placing the mic array over the band looking directly downward.  To do that I placed my big stand next to the drummer with the LS-3SAP extension extending vertically so that I could use the 90 degree oriented stud socket at the top to mount the mic array facing straight down.  That fit nicely and got the array in good proximity with a good stereo perspective, without it being a nuisance.  Only problem was the guitar and keys amps placed on the ground were then 90-degrees off axis and came across overly diffuse.  Made for a sweet recording of the drums though!
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 30, 2019, 12:22:09 PM
Fig-8 center-

I've not done it but expect Fig-8 to work well in the center position in the right situation.  Virtues are it's tight forward pattern as EmRR mentions, plus the general naturalness of sound quality from that pattern.  I find a good fig-8 is sort of like an omni in this way, both generally sound more natural and open to me than the intermediate patterns between these two basic patterns.  The challenge is the "right situation" part.

The potential problem is no control over front/back pickup balance, and getting that right is important.  The demarcation between too much and too little from the back is easy to hear when mixing and most of the time you'll want considerably less from the back than from the front.   That depends greatly on room and placement, but also on program material, with the total overall range of level from the rear somewhere between none to equal to that from the front. For sparser numbers and quiet sections, or between numbers, approximately equal sensitivity can sound the most natural - same for ambient environmental recording where equal sensitivity in all directions sounds most natural and is preferred unless additional focus is needed toward the direction of interest, or reduced sensitivity is needed in other directions.  For loud, dense material, less contribution from the rear is desirable, and of course if the rear direction is dominated by distracted chatter or other noise which overly distracts from the intended focus of the recording, you'd want less of that. 

I'd have to check a few mixes, but generally I start mixing with the rear channel(s) around -6dB down in comparison to the other "directions", and it may end up being -12dB or more.  Complicating that, I'm often raising level of the center channel in comparison to the other directions (sometimes substantially), so the front/back differential actually ends up greater than that.

So pattern tightness and naturalness from a fig-8 are good, but the lack of balance control means it may only be really good in some situations.  I think it could work well outdoors.  Indoors, one could maybe try placing a small baffle like a jecklin disk or something behind a forward facing center figure-8, but it would require trial and error and only provide a limited range of rear-sensitivity "tuning" determined prior to recording. 

Another strategy could be making the L/R pair more forward-directional to compensate for lack of forward directionality of the center microphone.   Maybe substitute forward-facing subcards or cardioids for the omnis.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 30, 2019, 12:37:19 PM
BTW, any recording made with Blumlein crossed fig-8s between spaced omnis can be mixed as if it were a 3-ch recording made with a single forward-facing 8 between omnis - by summing the L/R Blumlein channels together in equal amounts before mixing with the omnis.  This is equivalent to a Mid/Side manipulation which discards the Side channel information, leaving only a virtual figure-8 Mid. 

Rocksuitcase and Kindms recordings incorporating both OMT and AKG C426 in Blumlein from the same recording location come to mind.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on September 30, 2019, 01:42:15 PM
Grabbed an Impact LS-3SAP pole, seems unique in that it has a 2 way socket that'll give you a right angle, or remove the stud to used it as an extension.  I haven't noticed any other mention of this hardware around here. 

https://www.bhphotovideo.com/c/product/1339819-REG/impact_ls_3sap_adjustable_pole_with_socket.html (https://www.bhphotovideo.com/c/product/1339819-REG/impact_ls_3sap_adjustable_pole_with_socket.html)

That's the most recent one I picked up a while back.  Works well into a superclamp because it allows me to orient the extension either vertically or horizontally from the clamp. I most frequently use it in combination with one of these folding feet to create a short stand:

https://www.bhphotovideo.com/c/product/1119713-REG/impact_ls_3sb_backlight_stand_base.html (https://www.bhphotovideo.com/c/product/1119713-REG/impact_ls_3sb_backlight_stand_base.html)

A few weeks ago I played around with finding the best way to record a friends jazz trio at their regular outside patio gig.  No PA, and no real good place to put the rig without it being either overly distant or in the way directly in front of the band, so I tried placing the mic array over the band looking directly downward.  To do that I placed my big stand next to the drummer with the LS-3SAP extension extending vertically so that I could use the 90 degree oriented stud socket at the top to mount the mic array facing straight down.  That fit nicely and got the array in good proximity with a good stereo perspective, without it being a nuisance.  Only problem was the guitar and keys amps placed on the ground were then 90-degrees off axis and came across overly diffuse.  Made for a sweet recording of the drums though!

Cool, I like OH recordings many times. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: rocksuitcase on September 30, 2019, 01:46:12 PM
BTW, any recording made with Blumlein crossed fig-8s between spaced omnis can be mixed as if it were a 3-ch recording made with a single forward-facing 8 between omnis - by summing the L/R Blumlein channels together in equal amounts before mixing with the omnis.  This is equivalent to a Mid/Side manipulation which discards the Side channel information, leaving only a virtual figure-8 Mid. 

Rocksuitcase and Kindms recordings incorporating both OMT and AKG C426 in Blumlein from the same recording location come to mind.
https://taperssection.com/index.php?topic=192098.0              kickdown thread for the OMT 6 using the c426 in Blumlein.
https://taperssection.com/index.php?topic=192034.0              for rig pics                       
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on September 30, 2019, 01:49:09 PM
BTW, any recording made with Blumlein crossed fig-8s between spaced omnis can be mixed as if it were a 3-ch recording made with a single forward-facing 8 between omnis - by summing the L/R Blumlein channels together in equal amounts before mixing with the omnis.  This is equivalent to a Mid/Side manipulation which discards the Side channel information, leaving only a virtual figure-8 Mid. 

Yep.  Worth re-mentioning I've noticed you lose some top end info summing Blumlein, it really seems to work best as hard-panned information at least to my ears.  Contrast with turning Blumlein 45º so one is pointing mid, the other pointing side, and treating it as mid-side.  Then you are just picking side quantity.   

Either can be the better option, depending on placement/situation.  Blumlein might be advantageously PAS, or MS might be advantageously stage-centric. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 30, 2019, 04:24:20 PM
^ Yep.  Which gets back to my speculation concerning M/S or X/Y being the optimal coincident configuration in the center microphone position.  I image the optimal answer is PAS X/Y + stereo width adjustment as needed, while the more practical answer might be M/S + stereo width adjustment.. such as using a shotgun Mid, or in my case where the same recording array is intended for both 2ch and surround output, and there are additional L/R microphone pair(s) feeding the L and R speakers. 

That's because I only use center coincident-stereo in a 2ch mix, where I really have grown to like what it does.  For surround playback through a front L/C/R speaker arrangement, I use the Center Mid channel as a discrete Center speaker feed and the Center Side channel goes unused.  The irony is not lost on me that I actually end up recording one additional channel for the 2ch stereo mix that I am not using for 5.0 or higher-count surround output.  Granted that in a 2ch mix the levels of the the surround/ambient mic channels are significantly lower than what is used for surround through discrete speakers.

Thinking about it, I'd probably use the Center Side channel in any mix which uses two speakers for the primary playback stage across front- so I'd use it in 4ch quad mix if I ever did that, while for 3.0, 5.0, 7.0 or whatever where there is a center speaker in the playback arrangement, that Center Side channel goes used. 

..at least currently. Someday I'll play around with surround front stage mixing more thoroughly to determine if there is any benefit of using some of it to the L/R speakers of an L/C/R setup to improve seamless image blend across the front as it does in 2ch, or if that only adds unwanted cross-talk and combing.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on September 30, 2019, 05:01:17 PM
BTW, any recording made with Blumlein crossed fig-8s between spaced omnis can be mixed as if it were a 3-ch recording made with a single forward-facing 8 between omnis - by summing the L/R Blumlein channels together in equal amounts before mixing with the omnis.  This is equivalent to a Mid/Side manipulation which discards the Side channel information, leaving only a virtual figure-8 Mid. 

Rocksuitcase and Kindms recordings incorporating both OMT and AKG C426 in Blumlein from the same recording location come to mind.
https://taperssection.com/index.php?topic=192098.0              kickdown thread for the OMT 6 using the c426 in Blumlein.
https://taperssection.com/index.php?topic=192034.0              for rig pics                       

Thanks Kyle!  Mike's Blumlein sounds great on my cheap headphones at the office.  I'll try and give a listen to the OMT mix (and the Blumlein again) tonight or tomorrow at home.  A few questions on how you mixed the OMT-

Quote
ch1|2     AKGck22 omni spread 6 feet apart > Grace V2 >Tascam DR680|SD
ch3|4     AKG ck8 shotgun fwd 0'|AKGck61 cardioid rear 180' >Tascam DR680|SD
ch5|6     AKG c426 (Blumlein:fig8, 90) >V3 >HDP2 (24/48) >Tascam DR680|SD

Did you start with chs 1-4 and balance that first (as you normally would) before bringing in 5/6? Or did you start with the Blumlein and add the other channels to that?  Or some other mixing strategy?

What level relationship did you end up with between the fwd/rear pair and the Blumlein pair?
When adding the c426 to the mix, did you find you needed to adjust the balance between the front ck8 and the back ck61?
When adding the c426 to the mix, did you find you needed to adjust the balance between the center mics and omnis?
How was the c426 + omnis without the front/back pair?

And curious about any thoughts in general about the inclusion of Blumlein to the existing OCT4 arrangement you've been using and are familiar with, partly because I've really grown to love the pseudo-OCT near-spaced L/R supercards (now generally angled forward somewhat) and wonder if the Blumlein center does something similar.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: prepschoolalumniblues on September 30, 2019, 05:13:10 PM
Fig-8 center-

I've not done it but expect Fig-8 to work well in the center position in the right situation.  Virtues are it's tight forward pattern as EmRR mentions, plus the general naturalness of sound quality from that pattern.  I find a good fig-8 is sort of like an omni in this way, both generally sound more natural and open to me than the intermediate patterns between these two basic patterns.  The challenge is the "right situation" part.

The potential problem is no control over front/back pickup balance, and getting that right is important.  The demarcation between too much and too little from the back is easy to hear when mixing and most of the time you'll want considerably less from the back than from the front.   That depends greatly on room and placement, but also on program material, with the total overall range of level from the rear somewhere between none to equal to that from the front. For sparser numbers and quiet sections, or between numbers, approximately equal sensitivity can sound the most natural - same for ambient environmental recording where equal sensitivity in all directions sounds most natural and is preferred unless additional focus is needed toward the direction of interest, or reduced sensitivity is needed in other directions.  For loud, dense material, less contribution from the rear is desirable, and of course if the rear direction is dominated by distracted chatter or other noise which overly distracts from the intended focus of the recording, you'd want less of that. 

I'd have to check a few mixes, but generally I start mixing with the rear channel(s) around -6dB down in comparison to the other "directions", and it may end up being -12dB or more.  Complicating that, I'm often raising level of the center channel in comparison to the other directions (sometimes substantially), so the front/back differential actually ends up greater than that.

So pattern tightness and naturalness from a fig-8 are good, but the lack of balance control means it may only be really good in some situations.  I think it could work well outdoors.  Indoors, one could maybe try placing a small baffle like a jecklin disk or something behind a forward facing center figure-8, but it would require trial and error and only provide a limited range of rear-sensitivity "tuning" determined prior to recording. 

Another strategy could be making the L/R pair more forward-directional to compensate for lack of forward directionality of the center microphone.   Maybe substitute forward-facing subcards or cardioids for the omnis.

Thanks for the input. Backing up a bit, the reason this was on my mind is because I just bought a used Audio-Technica AT-4050 multi-pattern mic from the Yard Sale (omni, cardioid, figure-eight) thinking I would use it as a center cardioid between two omnis (all three going into a MixPre-3). I've never used a figure-eight before, though, so after looking it up, I started wondering about possibilities. I'll probably try out that configuration on a low-priority show just to see what it does (and will obviously report back).

And now I'm definitely curious about how a fig-8 between a directional stereo pair would sound too... maybe angling cardioids farther out than would normally make sense as a standalone pair, and then having a fig-8 low in the mix to provide some presence in the center (from both forward and rear perspectives)? I'm still trying to digest that Stereo Zoom paper, so my understanding of angles and spacing remains unhelpfully rudimentary...
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: rocksuitcase on September 30, 2019, 07:25:17 PM
Quote
Did you start with chs 1-4 and balance that first (as you normally would) before bringing in 5/6? Or did you start with the Blumlein and add the other channels to that?  Or some other mixing strategy?
Quote
For this show I actually mixed all six channels together. Typically, I would do a four or 5 channel mix using the center mic as my base point, but in this case with two centers available and given my crazy personal schedule I opted to do a "down and dirty mix". In the past, using all AKG mics, I've noticed mixing these specific set of sources to be very smooth compared to other sources we've used.  soooooooooo, in this specific instance:
I took all six channels in Audacity. In the master take channels 1|2 were at -2.5 dB (all levels approximate), channels 5|6 about -3.5 dB . channels 3|4 were at -8 dB or so.
                                                      It took three mixes to get what I found a decent compromise.

                                                    the final mix went like this (first, level adjust each pair; mono ch 3|4)
                                                      ch 1|2  were -2dB from master level =-4.5 dB
                                                      ch 3     was upped 4dB = -4dB
                                                      ch 4     was brought down -12dB = -20 dB
                                                      ch 5|6 down -1dB = -4.5 dB

What level relationship did you end up with between the fwd/rear pair and the Blumlein pair?
Quote
So I kept the mid ck8 in the final mix a bit lower than the Blumlein

When adding the c426 to the mix, did you find you needed to adjust the balance between the front ck8 and the back ck61?
Quote
the mix without c426 had a bit less "airiness" or natural room verb as the 426 added some accurate "envelopness" to my ears.
When adding the c426 to the mix, did you find you needed to adjust the balance between the center mics and omnis?
How was the c426 + omnis without the front/back pair?
Quote
That was a large amount of my listening before deciding to go with the down n dirty OMT6. I did two main listens:
1] I muted the c426 and listened to a different mix of omni vs fwd/rear.
2] Then muted the fwd|rear and listened to only fig 8 crossed plus omni.
                           The latter is a mix which should be tried out. As I said, this mix added some accurate "envelopness", some high frequency "pizazz" and a bit less in your face kick drum than the ck8/ck61 plus omni. (this ck8/ck61 fwd/rear has a bunch of kick drum and bass punch to my ears)
I should add that I could probably offer the raw files up via WT if any of you OMT folks re interested. Also that in discussing the mixing aspects with Lee over time, he knows and I agree that the possibilities and combinations of pairs, sub mixes and such can get overwhelming. In order to come out with a listenable 2 channel mix it is usually necessary to have a pallette of known good ideas/combinations and then let your ears guide you.  In this instance I did use all six channels in various levels. Often though one or more channels are not in the mix at all.

All critiques or listening opinions welcome for sure      8)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 01, 2019, 05:22:43 PM
Thanks for your mixing impressions.  I just downloaded and plan to give a listen tonight.

Quote
When adding the c426 to the mix, did you find you needed to adjust the balance between the front ck8 and the back ck61?
Quote
the mix without c426 had a bit less "airiness" or natural room verb as the 426 added some accurate "envelopness" to my ears.

This is interesting and makes sense.  I'm attempting to make a mental comparison to what the pseudo-OCT arranged L/R supercard pair adds to a 2ch mix in my OMT6 implementation, and I might describe that as "an increased sense of proximity to the source, presence enhancement and listening excitement".
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 01, 2019, 07:11:48 PM
Thanks for the input. Backing up a bit, the reason this was on my mind is because I just bought a used Audio-Technica AT-4050 multi-pattern mic from the Yard Sale (omni, cardioid, figure-eight) thinking I would use it as a center cardioid between two omnis (all three going into a MixPre-3). I've never used a figure-eight before, though, so after looking it up, I started wondering about possibilities. I'll probably try out that configuration on a low-priority show just to see what it does (and will obviously report back).

And now I'm definitely curious about how a fig-8 between a directional stereo pair would sound too... maybe angling cardioids farther out than would normally make sense as a standalone pair, and then having a fig-8 low in the mix to provide some presence in the center (from both forward and rear perspectives)? I'm still trying to digest that Stereo Zoom paper, so my understanding of angles and spacing remains unhelpfully rudimentary...

Try all three patterns to get a feel for them. Listen to that channel solo'd to get an idea of how the 8 and omni patterns in some ways sound more similar to each other than they do to the cardioid, yet sound different from each other in other ways.  Listen to the sound of what the mic is pointed at, but also listen to the sound of all the stuff the mic is pointed far away from. For me it helps to think of different pickup patterns not really so much as being tighter focused or more widely focused toward what they are pointed at, but rather how different patterns are less sensitive to sound arriving from various directions other than where the mic is pointed.  That may seem like word-play, but even the most directional microphone has a forward focus "window" at least 90 degree wide for the most part.

All three patterns can work between spaced omnis, or spaced cardioids.  We can talk about the differences between them here, but it will be most useful to simply hear the difference for yourself, in your own recordings.  Best to keep the omni spacing the same (3' apart is good if you can do that, say 2' minimum) while changing the center pattern.  If you can't space them as much as you'd like, use of the 8 in the center should help somewhat, as will switching the omnis to cardioids and pointing them outwards somewhat (PAS at minimum, +/- 45 degrees typical, on up to +/-180 degrees max).


The key idea underpinning all the Stereo Zoom stuff is the inverse relationship between microphone angle and spacing.  If we want to keep the intended pickup window (SRA or Stereo Recording Angle in SZ speak) the same, as spacing between a stereo pair of microphones is increased, the angle between them needs to be decreased.  And vice-versa.  As the spacing is reduced, the angle between microphones needs to be increased.

If we change the angle without making the inverse adjustment to spacing, or change spacing without changing the angle, the stereo pickup angle for the pair is changed.

In applying that to a 3 channel mic setup, it sometimes helps to think of it as two separate stereo pairs sharing one microphone in the center.  Each pair faces somewhat off-center so that their shared edge of their pickup angle joins up in the middle as long as the spacing/angle relationship between the two pairs is arranged correctly.  That may makes it easier to get a intuitive feeling for how the outside microphones of a 3-mic set need to be angled more widely than a stereo pair when the center shared microphone is pointing directly forward.. or alternately, the spacing between the outside mics and the center one needs to be increased.. or some combination of the two, in comparison to a stereo pair with the same pickup angle. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 02, 2019, 01:29:02 PM
https://taperssection.com/index.php?topic=192098.0              kickdown thread for the OMT 6 using the c426 in Blumlein.
https://taperssection.com/index.php?topic=192034.0              for rig pics                       

Oh yeah!

I totally dig Herring's projects along this line and lost myself in this last night listening on some good headphones.  Good stuff.

I pulled up both Mike's straight c426 Blumlein and Kyle's OMT6 incorporating the same, and went back and forth between the two.  At first I EQ'd as I felt necessary (partly headphone response correction), and was interested to compare how different the EQ curves might be that I ended up with for each, before switching my attention to more subtle aspects.  That varied from song to song, as well as between recordings, yet in the end the curves converged for the most part.  The two sound different, but I didn't really end up with an overall preference for one over the other.  I'd convince myself one was better, then switch and feel the same about the other.  Granted the the 426 blumlein pair in both sources made this less of a contrasting comparison and more of a straight Blumlein versus Blumlein + other channels type comparison.

One of the things that came to mind switching to the straight Blumlien was a feeling of "lushness yet uncomplicated purity".  It really does stand strong on its own.  The OMT mix including it excels in bass extension and envelopment, and in its slightly more diffuse portrayal of ambience and audience, almost hinting at another dimension. I sort of expected to hear sharper front imaging in the straight Blumlein, but I think it's inclusion in in OMT mix as well limited that potential difference between the two.

Quote from: gutbucket
How was the c426 + omnis without the front/back pair?
The latter is a mix which should be tried out. As I said, this mix added some accurate "envelopness", some high frequency "pizazz" and a bit less in your face kick drum than the ck8/ck61 plus omni. (this ck8/ck61 fwd/rear has a bunch of kick drum and bass punch to my ears)

Thinking out loud..

I speculate c426 + wide omnis alone might be an ideal 4ch recipe for that location in the Egg, and think it may be best to narrow the 90° Blumlein angle somewhat in that combination (this could be emulated to some degree with the existing raw files by making a M/S ratio adjustment to the blumlein pair). This would bring the fig-8's closer to on-axis with the front sources to help fill the role the OMT center mic plays, possibly making that channel unnecessary (unless you miss the the kick-drum and bass qualities you mention it contributing).  I expect that would also increase energy in the center and tighten up imaging across the middle, attributes I expect would be made better still combined with a slight pattern tweak to the 426.   Given the Blumlein's rear-lobe sensitivity, the rear-facing center mic is probably even less needed than it's front-facing partner.  Yet then the front/back ratio is "baked-in" by the polar pattern chosen for the 426 and it's hard to say how much shift in pattern incrementally toward hyper/super would get that balance just right (guessing one or two clicks on the pattern box away from 8 ).  You all have recorded there enough to probably develop a good feeling about that, and your OMT mix experience in dialing in an appropriate front/back balance at that recording position in that room is a key data point.

If you guys had to split for some inexplicable reason leaving me to set up your gear,  :'(  :P  ;) , I'd probably select hyper patterns one click away from fig-8 toward cardioid, narrow the included angle somewhat, and run that between the omnis. Idea being to get a bit more front focus from the 426 and let the omnis shoulder the ambient room/audience part a bit more, while still retaining plenty of rear lobe from the 426.  If I had a pair of supercards as well, I'd place them between the 426 and the omnis angled +/- 45° and narrow the 426 included angle further down to PAS, and we have coincident-center OMT6.

Heynow, thanks for letting me play with your gear, and so happy you both were able to make it back before showtime in my thought experiment! 

Hmm, maybe I should finally get around to sending the Peluso P-Stereo coincident LD mic back to John P for repair.

Thanks for the great listen last night!  That's good medicine for a taper's soul.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on October 02, 2019, 02:40:53 PM
Fig-8 center-

I've not done it but expect Fig-8 to work well in the center position in the right situation.  Virtues are it's tight forward pattern as EmRR mentions, plus the general naturalness of sound quality from that pattern.  I find a good fig-8 is sort of like an omni in this way, both generally sound more natural and open to me than the intermediate patterns between these two basic patterns.  The challenge is the "right situation" part.

The potential problem is no control over front/back pickup balance, and getting that right is important.  The demarcation between too much and too little from the back is easy to hear when mixing and most of the time you'll want considerably less from the back than from the front.   That depends greatly on room and placement, but also on program material, with the total overall range of level from the rear somewhere between none to equal to that from the front. For sparser numbers and quiet sections, or between numbers, approximately equal sensitivity can sound the most natural - same for ambient environmental recording where equal sensitivity in all directions sounds most natural and is preferred unless additional focus is needed toward the direction of interest, or reduced sensitivity is needed in other directions.  For loud, dense material, less contribution from the rear is desirable, and of course if the rear direction is dominated by distracted chatter or other noise which overly distracts from the intended focus of the recording, you'd want less of that. 

I'd have to check a few mixes, but generally I start mixing with the rear channel(s) around -6dB down in comparison to the other "directions", and it may end up being -12dB or more.  Complicating that, I'm often raising level of the center channel in comparison to the other directions (sometimes substantially), so the front/back differential actually ends up greater than that.

So pattern tightness and naturalness from a fig-8 are good, but the lack of balance control means it may only be really good in some situations.  I think it could work well outdoors.  Indoors, one could maybe try placing a small baffle like a jecklin disk or something behind a forward facing center figure-8, but it would require trial and error and only provide a limited range of rear-sensitivity "tuning" determined prior to recording. 

Another strategy could be making the L/R pair more forward-directional to compensate for lack of forward directionality of the center microphone.   Maybe substitute forward-facing subcards or cardioids for the omnis.

Couldn't one adjust the front/rear balance of a figure 8 center by doing the same sort of processing one does when "manually" mixing down to mid-side?  Reverse polarity of the figure 8, etc?
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: rocksuitcase on October 02, 2019, 02:42:03 PM
Quote
I speculate c426 + wide omnis alone might be an ideal 4ch recipe for that location in the Egg, and think it may be best to narrow the 90° Blumlein angle somewhat in that combination (this could be emulated to some degree with the existing raw files by making a M/S ratio adjustment to the blumlein pair).
Thanks for the positive reviews! To address this specific mention briefly: Iagree ideally for OMT techniques that a center Blumlein pair should eb narrowed to at least PAS if not 50-60 degrees. The physics of it would offer a much more solid center tonality plus allowing the omnis to have a bit more decorrelation between them and center.

The main reason we do not do this recently is that we are also making a "Safety" or distinctly different recording with the 2 channel 426. I was going to suggest this to kindms before we went into the theater but sort of pushed it aside and went with the safety theory aspect. Also, If channels or space were restricted, I would definitely do only the 426 center with omnis outside (DPA 4060's if space was that tight). I also agree that in this instance I could have left off the ck8 center, kept the ck61 rear and the spaciousness would be there with a bit less defined center image.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 02, 2019, 04:47:38 PM
The main reason we do not do this recently is that we are also making a "Safety" or distinctly different recording with the 2 channel 426. I was going to suggest this to kindms before we went into the theater but sort of pushed it aside and went with the safety theory aspect.

A wise choice I think, and one I assumed fit the MO of the everyone involved.  And great to have that straight Blumlein pull as a baseline for comparison. We've talked in these threads before about the additional leap of faith and potential dangers involved with abandoning the "safety" to go all out.



Couldn't one adjust the front/rear balance of a figure 8 center by doing the same sort of processing one does when "manually" mixing down to mid-side?  Reverse polarity of the figure 8, etc?

Only if you had an omni coincident with it to do "Polar-flex" style M/S.  Then you could choose any pattern facing directly forward and rearward.

With a single fig-8 in the middle between the wide-spaced omnis, flipping its polarity won't do much.   It may change the sound as it changes it's phase/polarity relationship with the omnis, but that phase relationship is already  highly randomized at high frequencies.  I expect you might get more mid bass cancellation in one polarity orientation versus the other.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on October 02, 2019, 04:57:04 PM
Couldn't one adjust the front/rear balance of a figure 8 center by doing the same sort of processing one does when "manually" mixing down to mid-side?  Reverse polarity of the figure 8, etc?

Only if you had an omni coincident with it to do "Polar-flex" style M/S.  Then you could choose any pattern facing directly forward and rearward.

With a single fig-8 in the middle between the wide-spaced omnis, flipping its polarity won't do much.   It may change the sound as it changes it's phase/polarity relationship with the omnis, but that phase relationship is already  highly randomized at high frequencies.  I expect you might get more mid bass cancellation in one polarity orientation versus the other.

I'm probably just revealing my own ignorance here, and it's been a bit since I manually did a mid-side mix, but can't the figure 8 channel alone be used to make discrete left and right channels?  I'm struggling to remember if that's how it worked.  If so, though, the front lobe would end up in one channel, with the rear lobe in the other, and the level of each could be adjusted then mixed back down to one channel right?

I feel like it's entirely possible that I'm so off base here I come across as not much different than a crazy person standing on the corner yelling at traffic.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on October 02, 2019, 06:06:59 PM
It's only when that output signal is sum/difference mixed with another phase-correlated signal (from a second coincidently-placed microphone) with a different directional orientation, that you get an output of two signals with different directional vectors. <meaning normalish patterns facing in particular directions.

Bingo.  That's the part I was forgetting.  Sorry for wasting everyone's time, and thanks for setting me straight.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 02, 2019, 06:13:50 PM
No worries.

[edit- oops accidentally deleted this post while editing it to add the pseudo-stereo stuff (which is now in the post that follows this one), so I'm reposting it here]

Dude, watch out for that garbage truck!

No. Its only a single channel.  The mic doesn't really know which direction it is facing and is equally sensitive to both directions. The front positive-polarity lobe and the rear negative-polarity lobe are "mixed together" in the output.  If you flip polarity the microphone is still facing both ways, except the waveform is inverted.

It's only when that output signal is sum/difference mixed with another phase-correlated signal (from a second coincidently-placed microphone) with a different directional orientation, that you get an output of two signals with different directional vectors. <meaning normalish patterns facing in particular directions.


You might be thinking of how some bidirectional microphones are formed by the differential summing of two well-matched back to back cardioid elements.  But in this case it's really two microphones facing opposite directions.  Typically the summing is done in the microphone and there is only a single output (the omni component of the two cardioids cancels out, leaving just the sum of the bi-directional components of the cardioids), yet some mics have outputs for the individual capsule which allows to you do the differential summing in the mixer, or use the outputs directly as two back to back cardioids. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 02, 2019, 06:19:22 PM
Quote
It's only when that output signal is sum/difference mixed with another phase-correlated signal (from a second coincidently-placed microphone) with a different directional orientation, that you get an output of two signals with different directional vectors. <meaning normalish patterns facing in particular directions.

^ I struggled with the wording there.  You can do mid/side sum/difference processing of any two signals and they needn't be phase-correlated with each other.  But if they aren't you won't be synthesizing well-behaved 1st order virtual polar patterns. 

I've posted in these threads about using the rear-facing mic as Side channel in combination with the forward facing Mid.  Doing that "pseudo-stereoizes" the single rear-facing channel, but that doesn't equate to virtual X/Y hypercards or whatever.  If you could plot out a polar that would probably look something like an exploding asterisk at mid and high frequencies, varying with frequency.  At low frequencies where the spacing between the two mics is acoustically insignificant, you'd get summing to omni in the left channel and differential summing toward null (though not perfectly) in the right channel, which is exactly how it is supposed to work for M/S with coincident channels (they are effectively coincident for long wavelengths), yet is a problem with that sterilization technique.  Fixes for that could be monoizing below a the frequency where the two start to come into phase correlation, or using a +90° phase-shift on the left channel copy and -90° phase-shift on the right channel copy rather than flipping polarity of the right channel copy 180°.  That achieves the same 180° relationship between the two Side channel copies yet in a way that is phase-symmetrical so the bass doesn't all go left.  It's how basic 4:1 LCRS matrix surround encoding worked still works to fold the surround channel information into LtRt

Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on October 03, 2019, 01:26:13 PM
Sorry for little different topic. I recently encountered a little trouble when I was fine-tuning OMT mix.

A simple example - when I try to add e.g. +3db of center mic to the mix, the overall volume increases. Then it is difficult to compare new and old version because it is not the same volume. I tried to solve it in DAW by creating a group of two tracks. One with + 3dB center mic and the second with reverse polarity of spaced omni. I set the volume of reverse polarity omni track to compensate the add of +3dB center mic. When I turn this group on or off, the overall volume is the same, but the center and spaced mics ratio is different.

It's a complicated, maybe it's useless. But I had the feeling that it helped me to make decisions. I wonder if anyone has easy solution for this when mixing OMT.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 03, 2019, 03:53:30 PM
Most of the time I tend to just make quick ball-park fader adjustments of all channels in question when determining the most appropriate balances, combined with liberal use of the mute and solo buttons.  But your reverse polarity trick to lower the level of the pair is clever!  I've occasionally done something similar by just making a straight (non-inverted) copy of whatever channels I want to adjust simultaneously and unmuting that group when the corresponding group is muted.  However, your method allows for a more accurately adjusted comparison with a single button push.. as well as allowing for the fine tuning of that balance by adjusting the level of the linked group.

The general idea behind this kind of "maintained energy balance across all channels while making an adjustment" approach is something I've wanted implemented in multichannel editors for years.  In addition to tweaking level balances that way, I'd like to be able to make fine EQ and other filtering adjustments this way as well.   An EQ change in the target channel(s) would impart a corresponding "energy balanced" inverse change in all non-target channels, such that the overall frequency balance of the entire mix remains the same as the EQ bias is shifted between sources.  Not only do I feel this would be super beneficial in the 'tweaking stage' once a good rough balance is in place, making the process of finding an optimal balance considerably quicker and easier,  I believe it would open up powerful new approaches to sweetening the mix.  I do some of this kind of balanced trade-off tweaking now, but its a hassle to try and keep the overall balance unchanged while playing with the variations.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on October 03, 2019, 05:17:25 PM
However, your method allows for a more accurately adjusted comparison with a single button push.. as well as allowing for the fine tuning of that balance by adjusting the level of the linked group.

Yes, I need a single button push for comparison. This is helping me a lot because my listening skills are low.

The general idea behind this kind of "maintained energy balance across all channels while making an adjustment" approach is something I've wanted implemented in multichannel editors for years.  In addition to tweaking level balances that way, I'd like to be able to make fine EQ and other filtering adjustments this way as well.   An EQ change in the target channel(s) would impart a corresponding "energy balanced" inverse change in all non-target channels, such that the overall frequency balance of the entire mix remains the same as the EQ bias is shifted between sources.  Not only do I feel this would be super beneficial in the 'tweaking stage' once a good rough balance is in place, making the process of finding an optimal balance considerably quicker and easier,  I believe it would open up powerful new approaches to sweetening the mix.  I do some of this kind of balanced trade-off tweaking now, but its a hassle to try and keep the overall balance unchanged while playing with the variations.

You mentioned this in some previous posts and you inspired me. I have been using a lot reversed tilt eq. It shows me how individual microphone pairs contribute to the overall mix and what to improve. And I usually use this reverse tilt eq (+- 1dB) in final mix too.  It is possible to make reversed classic eq, mid/side manipulations or any plugin in Reaper. But tilt eq is easy and very effective for me.

For those who use Reaper - there is possibility to link all plugins parameters and set their relationship, e.g. inverse change. The procedure is very simply.
1. prepare reverse plugin - Load two plugins, link the parameters and save these plugins as FX chain.
2. use reverse plugin - Load this chain, bundle the first plugin with channels 1, 2 (e.g. center xy pair) and the second plugin with channels 3, 4 (e.g. spaced pair). Now, the change in one plugin will appear in the other mirrored opposite.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 03, 2019, 05:33:59 PM
I dig tilt type EQ.  It's a "superwide Q totally tonal" type of thing.   Sounds good and reveals basic frequency balance relationships quickly. Surprised its not seen more often.

Thanks for outlining the inverse-change plugin method for Reaper. Very cool that reverse-plugin is available there.  Maybe I should look at Reaper again, but I don't really want to relearn my way around another editor.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on October 03, 2019, 05:55:12 PM
I understand this very well, I don't want to learn another DAW too. I think there is a good chance that other software developers will also add the ability to link parameters. It shouldn't be difficult and this function is useful.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: rocksuitcase on October 04, 2019, 09:24:17 AM
Sorry for little different topic. I recently encountered a little trouble when I was fine-tuning OMT mix.

A simple example - when I try to add e.g. +3db of center mic to the mix, the overall volume increases. Then it is difficult to compare new and old version because it is not the same volume. I tried to solve it in DAW by creating a group of two tracks. One with + 3dB center mic and the second with reverse polarity of spaced omni. I set the volume of reverse polarity omni track to compensate the add of +3dB center mic. When I turn this group on or off, the overall volume is the same, but the center and spaced mics ratio is different.

It's a complicated, maybe it's useless. But I had the feeling that it helped me to make decisions. I wonder if anyone has easy solution for this when mixing OMT.
kuba, I understand this. Using Audacity, I am mostly like Gutbucket in that I generally throw on the 4 or 6 channels, check for overall level and balance the stereo pairs (or mono channels if fwd|rear), then adjust each channel's sliders and then use mute and solo to isolate what I like or don't and maybe go in and change a slider up or down a few times. once settled on something which sounds solid, with good centering in both headphones and my basic desktop speakers and export to a stereo mix, naming this roughmixXX.
SO I am not doing the type of additions you are, however, I DO understand your issue. It seems like doing a single button inverted polarity is a good way to go.
On this note, I am thinking of having to add Izotope for at least some mastering tools, and am a bit tentative over the learning curve.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on October 06, 2019, 04:45:45 AM
Kyle, I am doing mix like you and Gutbucket. I had two cases when I was totally unsure and I needed fine tuning. One case was too little spaced omnis. I wanted to mix the center cardiod in, but it didn't sound good. I was trying to add just little bit and also to stereoize the center mic. But in the end the best variation was plain omni. The second case, when I'm not sure at times, is mixing the rear channel. It seemed to me that the rear channel is adding great third dimension but also we may sometimes lose a little bit of clarity. These cases are only about details and are not worth the effort. The only positive is that I practice listening.

On this note, I am thinking of having to add Izotope for at least some mastering tools, and am a bit tentative over the learning curve.

I have some cheap pack of Izotope basic plugins. From what I see it is very user friendly. The best is to try it before you buy it, they offer one moth free. They'll probably offer you a discount for purchase too.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 07, 2019, 12:11:49 PM
One case was too little spaced omnis. I wanted to mix the center cardiod in, but it didn't sound good. I was trying to add just little bit and also to stereoize the center mic. But in the end the best variation was plain omni.


This makes sense.  You could try increasing stereo width of the omni pair to "make room for the center cardioid" in the mix.  Doing so increases the difference information between omni channels and decreases the monophonic sum information shared between channels.  It's that shared mono-sum info that is in conflict with the center cardioid.  Probably don't want to push that too far, but worth a try, if only to hear what it does.

Quote
The second case, when I'm not sure at times, is mixing the rear channel. It seemed to me that the rear channel is adding great third dimension but also we may sometimes lose a little bit of clarity.


This is a good description of the general trade off when determining the appropriate contribution from the rear-facing mic(s) in a stereo mix.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 18, 2019, 11:59:24 AM
Was re-reading Hyunkook Lee's comments on MARRS, which we've discussed in the past elsewhere at TS along with other stereo imaging visualization tools leveraging Stereo Zoom and similar research, and the following jumped out at me (note- my bold, italics and underlining, and ellipsis below) :

Quote
MARRS (Microphone Array Recording and Reproduction Simulator) is an interactive and intelligent tool for stereo microphone technique simulation. It allows the user to predict the perceived positions of multiple sound sources for a given microphone configuration. The tool can also automatically configure suitable microphone arrays for the user’s desired spatial scene in reproduction.
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The app can recommend you a range of correct microphone configurations for a desired overall stereo width of the ensemble you are recording... MARRS will then calculate the correct angle and spacing of a microphone array that you need to apply for the desired stereo width... Note that you still have a control over “what type of array” you want it to be. The “XY/AB” section in the configuration view allows you to determine the ratio between 100% coincident (XY) and 100% spaced (AB) depending on the desired spatial characteristics of the stereo image. The more XY you apply, the image will tend to get more localizable but less spacious. The more AB you apply, the image will tend to sound more spacious but less sharp and localizable. Near-coincident techniques such as ORTF and NOS benefit from both localizability and spaciousness. They are popular “preset” techniques with a fixed XY/AB ratio, but you can flexibly choose the ratio, thus designing your own near-coincident technique, depending on your purpose using MARRS.

This echos the statements I frequently make at TS about near-spaced stereo microphone pair techniques representing various "preset, hopefully best compromise" stereo arrangements.  We are able to bias that compromise one way or another by how we set up, informed by experience and tools such as SZ, the Improved-PAS table, MARRS, etc, yet at that point the compromise becomes fixed, prior to recording.  One of the advantages of OMT arrangements which combine a spaced pair and a coincident center pair (with or without additional near-spaced channels) is that we record both and gain control over the blend of stereo characteristics after the recording has been made.   But more than that, when done well I find I can achieve a combination of otherwise disparate stereo aspects which is unachievable by near-spaced stereo "compromise" arrangements on their own.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on October 21, 2019, 10:45:59 PM
If I ever saw this info, I'd forgotten it:

Quote
The ear uses mainly two techniques for determining directional information in a horizontal plane: differences in level and differences in time of arrival/phase between the two eardrums. When listening to complex waveforms, both methods help in localization. With respect to frequency, however, the application of one of these two techniques usually excludes the other.

The following paragraphs on localization are informed by the excellent text on psychoacoustics by J. Blauert:

In the low frequency range up to about 800 Hz, the human brain depends mostly on phase information for localization purposes. This figure of 800 Hz coincides to a wavelength of approximately 1.25 feet. Not coincidentally, this length of 1.25 feet corresponds to about twice the greatest length between a pair of human eardrums. In other words, for frequencies below 800 Hz, the phase of the impending sound at the nearer ear always leads the phase of the sound at the farther ear by less than 180 degrees. Such a close phase relationship between the sounds heard at both eardrums creates an unambiguous method for localization. The phase difference is linear with respect to frequency, thus also aiding with the ear’s attempts at discerning the spectrum of an incoming sound.

For frequencies above 1.6 kHz (the high frequency area), phase relationships between the eardrums become meaningless. Since the period of such frequencies is less than the amount of time sound takes to travel between the ears, phase relationships between sounds at the ears will be misleading, shifting through a full 360 degrees for every octave. In this range, therefore, the brain must depend on level and time differences between the ears for localization purposes. This method relies somewhat on the diffraction and absorption qualities of the head itself. Off center high frequencies will hit the nearer eardrum with no loss in level, but upon encountering the head as an acoustic obstacle, can fall several decibels before reaching the following eardrum. In certain combinations of direction and frequency, this attenuation can exceed 20 decibels!

As of yet unmentioned has been the frequency range from 800 Hz to 1.6 kHz, the middle area for localization. Perhaps middle area is the wrong term; gray area may be more appropriate. In this region, level differences between the ears are not very effective since the wavelengths are very long in comparison to the size of the head. Also, phase differences are misleading because they now exceed 180 degrees between the ears; the closer ear, therefore, now lags in phase behind the further ear. The brain must thus use a combination of these two methods (phase and level) to localize sound. In practice, however, the localizing ability within this frequency range is basically not good.

The discussion of localization so far has focused on frequency ranges and thus relates to periodic sine wave sources. Such information, however, only allows for an estimation of the ear’s true abilities of perception for aperiodic signals like music, speech, or any other real world sounds. The sustained portion of sound from musical instruments can be characterized as sinusoidal, and much of the ear’s methods for localizing such portions of sound are as previously described. The attack portion of sound from instruments, especially percussion instruments, however, is most often impulse based. For such quick transients, pure time of arrival differences between the ears are used to localize the source. In other words, direction is determined solely by whichever ear first hears the impulse.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: thunderbolt on October 22, 2019, 08:04:58 PM
I picked up a used Pearl MSH-10.  I have not used it in a concert setting yet but am going to try it next month for grins with a primary pair of 41s.  New venue for me (Sherman Th., Stroudsburg, PA).  I’ll post a clip after.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on October 22, 2019, 08:39:10 PM
I picked up a used Pearl MSH-10.  I have not used it in a concert setting yet but am going to try it next month for grins with a primary pair of 41s.  New venue for me (Sherman Th., Stroudsburg, PA).  I’ll post a clip after.

oh cool! 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 29, 2019, 05:41:00 PM
^ Congrats. That Pearl looks to be a sweet microphone.  Should be interesting.

Kuba, Following up on your previous post..  There is no reason you must use all of the channels you've recorded in your mix. It's fun to discuss the technical possibilities and options, but if it sounds best with just the omni pair, no problem to just let it be. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on November 02, 2019, 12:25:18 PM
Following up on this post ( a few back):
http://taperssection.com/index.php?topic=191953.msg2314309#msg2314309

I had a thunderstorm roll through the other night and put out a Blumlein pair with a 30" AB omni pair.  In post I tried a 6dB/oct crossover between the pairs at 1200Hz, and it sure seems to do the right things to clear up the differences between the two pickups.  Listening to the two pairs separately, it's wild how totally different they are.  Without the crossover, the combined pairs seem cloudier and thicker, with obviously competing information. 

(https://live.staticflickr.com/65535/49002269571_ffa25208b9_c.jpg)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on November 04, 2019, 05:20:54 PM
Cool.  Did you determine the crossover frequency beforehand or decide upon it by shifting it up/down and listening for best effect?  If determined by listening, how broad was the region in which there was little significant difference?

There are a few things in play here.  On the listening side- the Duplex theory of localization, on the recording side the AB omni spacing and its relation with wavelength, stereo recording angle, and the frequency above which pickup of diffuse sound becomes decorrelated.

Would be interesting to compare this to the same setup with a 2-3 times wider AB spacing if you get the chance.  The "texbook" Stereo Recording Angle of significantly wider AB omni spacings would no longer be as close to that of the Blumlein pair as they are in this case (where both are within 10° as indicated by the sengpielaudio visualizer; 90° Blumlein ~= 75° SRA; 30" AB omni ~= 85° SRA) but the SRA of omnis is pretty loose to begin with, especially at wide angles, and would only become more so only across a partial frequency range, presumably.

Increased AB spacing will lower the diffuse pickup decorrelation frequency between the two omnis, but also between the Blumlein pair and each omni (half the distance - twice the frequency) which reduces the phase interaction between pairs that is likely to be a leading contributor to a "cloudier & thicker" sound. 

I suspect this kind of carefully tuned crossover technique may be most advantageous for blending pairs that have similar SRAs and are less widely separated from each other.  It represents sort of a "dual-element main pair incorporating a careful hand-off that avoids conflict", rather than a mix of two pairs with different strengths that accentuate each other with somewhat less inherent conflict.

I tried and dismissed the "similar SRA's" approach in building up OMT arrays, but never got around to implementing a crossover to manage the hand-off, and that is what I suspect is required for such an approach to work correctly.  Thanks for posting about it here.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on November 04, 2019, 05:58:15 PM
Did you determine the crossover frequency beforehand or decide upon it by shifting it up/down and listening for best effect?

Very basic experiment; picked 1200Hz at 6dB/oct as a test and went with it.  Haven't done anything else besides listening to individual pairs and all 4 blended with no crossover - had about 20 spare minutes to run post on it the other day, no chance so far to revisit. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on November 09, 2019, 10:33:58 AM
Went back and checked it again, tried lower and higher crossover points.  Can hear a subtle difference.  The experiment seems to corroborate the 'science' of the zone between 800 and 1600. 

I don't find any way to sweep and listen, given that it's separate HPF and LPF EQ's set to the same frequency on different sources, and mixed.  An assembled crossover for mixing, rather than splitting. 

I will try closer and wider AB spacing, my gut reaction listening to the two types separately is that wider spacing will begin to create too much shift between types in this particular approach. 

Concert taping would seem to throw most of these 'rules' out the window anyway. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on November 11, 2019, 12:35:56 PM
All makes sense to my way of thinking.

I've posted previously about how I wish mix/editing software packages would provide an easy way to setup this kind of complementary/inverse filtering to allow simultaneous adjustment of both filters with a single control.  Would make homing in on sweet points while mixing much easier.  This is yet another good application for such a feature.

This kind of crossover filtering between multiple mics in an array has been done by others but is not that well explored or documented around TS and I've not really had the chance to play with it as much as I'd like.  Thanks for posting your observations.

Similar but not exactly the same- a long ago I imagined applied a frequency-specific microphone-crossover technique to a bunch of omnis arranged in a line.  Imagine 6 or 8 omnis in a line with progressively increased spacing between pairs- a near-spaced HF pair in the middle, a mid-spaced midrange pair flanking that, a wide-spaced LF pair outside of that.. and crossover frequencies determined by the spacining relationships.  Such a setup really would make a simplified "phased array", linking wavelength and cross-over frequency and producing a similar SRA for each frequency range.

Next thought experiment added a baffle between the center pair.. And then a shift to use of increasingly directional microphones at the narrower spacings.  Imagining a high-passed 90° X/Y supercard pair + a high-mid band-passed near-spaced 90° cardioid pair + a low-mid band-passed mid-spaced 90° sub-cardioid pair + a wide-spaced low-passed omni pair.

Oddball for sure!
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on November 11, 2019, 02:02:51 PM
Similar but not exactly the same- a long ago I imagined applied a frequency-specific microphone-crossover technique to a bunch of omnis arranged in a line.  Imagine 6 or 8 omnis in a line with progressively increased spacing between pairs- a near-spaced HF pair in the middle, a mid-spaced midrange pair flanking that, a wide-spaced LF pair outside of that.. and crossover frequencies determined by the spacining relationships.  Such a setup really would make a simplified "phased array", linking wavelength and cross-over frequency and producing a similar SRA for each frequency range.

Next thought experiment added a baffle between the center pair.. And then a shift to use of increasingly directional microphones at the narrower spacings.  Imagining a high-passed 90° X/Y supercard pair + a high-mid band-passed near-spaced 90° cardioid pair + a low-mid band-passed mid-spaced 90° sub-cardioid pair + a wide-spaced low-passed omni pair.

Oddball for sure!

You're gonna have to try that!
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on November 11, 2019, 03:48:16 PM
Just intended as something interesting to think about, exploring the idea.. not really meaning to suggest you actually do it!

I would still like to give it a go out of curiosity, but doubt I ever will.  If I ever do it would probably be at the amphitheater where I've run all my other crazy test setups over the years.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: mfrench on November 12, 2019, 04:51:41 PM
This one worked really well.
Both a 4.mic coincidental (dr70d arry) and 6mic (binaural tracks added) renderings.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on November 12, 2019, 05:47:26 PM
^ Truly oddball! er, oddbox!
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: mfrench on November 12, 2019, 10:40:40 PM
I wanted to try to get in close to the seated mid-section.  So I used the rearwardly baffled PZM-BLE pair as the forward pair there.  I used the CM3 as the rearward facing pair to pick up the rest of the ensemble, out to the outer points.
I cannot express enough what a mind screw it was to try to remember to keep the rearward pair in proper relation to the forward pair. Everything in my being had me trying to cross-connect them in hook up.
I've been liking the coincidental aspect in mixing.  It seems to me that it reduces a lot of the timing offest error that you get with NC patterns, in mixing. Its a lot cleaner insertion. With the omnis being this close, they might as well be thought of as coincidnetally timed. The baffling does the rest there. And with the directionality of the CM3's, it left that area well enough attenuated that it wasn't being redundant, and cancelling.
I liked it, quite a lot. I'm not sure when I could use it again, but I will, for sure.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on November 13, 2019, 09:55:14 AM
Dig it.  Whatever works!
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on November 13, 2019, 11:54:10 AM
I wanted to try to get in close to the seated mid-section.  So I used the rearwardly baffled PZM-BLE pair as the forward pair there.  I used the CM3 as the rearward facing pair to pick up the rest of the ensemble, out to the outer points.
I cannot express enough what a mind screw it was to try to remember to keep the rearward pair in proper relation to the forward pair. Everything in my being had me trying to cross-connect them in hook up.
I've been liking the coincidental aspect in mixing.  It seems to me that it reduces a lot of the timing offest error that you get with NC patterns, in mixing. Its a lot cleaner insertion. With the omnis being this close, they might as well be thought of as coincidnetally timed. The baffling does the rest there. And with the directionality of the CM3's, it left that area well enough attenuated that it wasn't being redundant, and cancelling.
I liked it, quite a lot. I'm not sure when I could use it again, but I will, for sure.

Have you ever tried omnis on all four sides of that box?
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: mfrench on November 13, 2019, 12:43:20 PM
No. But I like your thinking.
This is the second time I've used the box as a PZM-BLE array.  The first time was with this same ensemble, and, was in combination with a 0º / 180º cm3 array over the top of it. That time I also had Güde Head mounted on top of the box, instead of the XY/CM3 array. The box is his road/storage box, and, chest/torso box.
Your question did just cause me to break out the MKE2002 mics, and see how they would fit. They wold work well, but would need some other form of attachment, and, they'd never be able to mount as tightly as the MKE2 pair.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on November 13, 2019, 03:34:59 PM
Have you ever tried omnis on all four sides of that box?

Do it! In my experience this works extremely well.  It is in essence a loose description of my "other" OMT rig which I don't post about, is the setup I run most often, and why I commissioned Chris Church to build a custom 4-ch CA-UGLY2 preamp years ago for use into a DR2d.

Differences are use of a rectangular rather than square "chest/torso box", rotated 45° to form a Left/Center/Right/Back configuration rather than 4-corner quad-like arrangement, with four DPA 4060 in the DPA boundary mounts, one at the center of each face.  This was the inspiration for my initial experimentation with the original OMT4 array that extended a basic pair of spaced omnis to a sort of diamond-shaped Decca-tree rather than the traditional triangle-shaped Decca tree, using 1m spacing and sphere-mounted omnis rather than flying a big rectangular box atop a stand.  The effect of the wide rectangular baffle box became even better emulated by substitution of the directional front/rear-facing center pair between the wide-spaced omnis rather than using 4 omnis all around, and eliminated the need for as much front/back spacing.

I'm sure folks following this thread can envision what I'm getting at, but PM me if you'd like clarification.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on November 13, 2019, 05:00:36 PM
Off-center setup/config for specific room (http://taperssection.com/index.php?topic=185036.msg2252341#msg2252341)
^ I may have posted a link to this in the previous OMT thread, but am linking it here after Heathan cited it today in another thread.

Good discussion and examples of thoughtfully applied odd setup techniques for the common halfway back and off-center recording position in a hardwalled room problem.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on November 19, 2019, 09:01:29 PM
With a PAS shotgun approach in a fairly small indoor room like I tried, I gotta wonder if there is value in using only one, pointed directly at the closest stack rather than at the center of the stage, then mixing it in the center of another stereo array.  It's usually vocal register stuff I'm missing, and dead on the stage adds more drums than anything, which is NOT the deficit in the other arrays. 

I noticed a Rycote mount meant for mounting to 1/4" camera points that looked like a possibility for this, combined with a clamp, since it has a swing arm with some slide positioning.  It's definitely fiddly to get positioned coincident but seems like a solution.   I can see I may end up machining a replacement swing arm of greater length and slide to really get this where I want it.   Full rig in a post below.

(https://live.staticflickr.com/65535/49098531022_4055b4724f_c.jpg)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on November 20, 2019, 10:59:08 AM
I like where that is going.  I thought I had commented previously on the bit below, but maybe that was only in my own mind since we were talking about other things as well..

With a PAS shotgun approach in a fairly small indoor room like I tried, I gotta wonder if there is value in using only one, pointed directly at the closest stack rather than at the center of the stage, then mixing it in the center of another stereo array.  It's usually vocal register stuff I'm missing, and dead on the stage adds more drums than anything, which is NOT the deficit in the other arrays.

Yes!  My justification for a shotgun over a better behaved pattern is the push for maximum possible pickup of direct-arrival sound for good clarity, most often needed for vocal register stuff as you mention.  It seems odd to intentionally make the array asymmetrical by pointing the directional center microphone somewhat off-axis from the rest of the array, but one can think of it as a further "division of labor" or differentiation of tasks that OMT is built around to begin with.

Before I moved to a M/S center pair (which in my current setup is more or less fixed in a directly-forward pointing direction with respect to the other mics in the array), I had the center mic on a telescopic TV antenna that gimballed at its attachment point, and sometimes pointed the center microphone in a direction other than straight-ahead with respect to the rest of the array.  I usually did that when presented with an awkward recording location that did not allow the wide-dimension of the array to be perpendicular to the axis along on which I wanted the directional center microphone to point.  Or sometimes up on-stage or stage-lip for non-PA amplified instrumental acts where I'd orient the entire array with respect to the ensemble, then point the center mic up and over at the snare rather than at the kick-drum.  The first few times I did this I was concerned about causing an image imbalance, but was pleasantly surprised to find that wasn't a problem.  The stereo image is initially set by the orientation of the primary wide-dimension of the array, and strongly influenced by manipulation of balance level of the Right/Left assigned array channels in the mix.  Angling the single directional center microphone away from directly forward did not shift the imaging at all, it only affected the quality of sound populating the center of the playback image.  That was not initially intuitive, but makes sense considering image placement of a single center microphone is determined to some extent by its spacing relationship with respect to the other microphones, and to a greater extent by its panned balance position in the mix.  If panned to center, it's content is going to fill the center of the playback image regardless of where it's pointed.  It needn't even be a member of the array.. or even share the same content.  Consider a voice-over mixed to center.  It fills the playback center image but isn't otherwise related to the stereo content it overlays at all.

Your setup above takes this a couple steps further.  1st by achieving maximum on-axis focus in that channel by using a shotgun mic, and 2nd by retaining a M/S or X/Y center pair as part of the rest of the array with the angled single PAS shotgun coincident to that.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on November 20, 2019, 11:08:54 AM
How important is that? Dunno, this is new territory.

It raises these questions in my mind:
Can we eliminate the center pair by just using the fig-8 in combination with the PAS-angled shotgun for M/S?
If so, should the fig-8 remain perpendicular to the rest of the array (which is the basis of stereo orientation for the array), or to the angled shotgun?
^
I'll have to think some more about that one.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on November 20, 2019, 11:49:14 AM
You couldn't find your original response because the quote started over in that ORTF + omni thread. 

I'll certainly listen to the shotgun as the M of the MS pair to see.  I am guessing the directionality may make the image weigh to one side, because of the weighting of information in the MS encoding. 

Separately I am curious to see how the spot shotgun addition to an MS pair blends.  I can see there being some dynamic bleed artifacts with things having temporary wider bursts that swim around.  Possible the shotgun will need LPF/HPF to tailor blend, on top of needing to have a minimal blend level to achieve spotting without overwhelming the main MS. 

Looks like a 7 mic array test coming up.....
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on November 20, 2019, 08:42:23 PM
Theoretical 7 channel rig build.   THAT took awhile to configure.  I'm hoping the angled shotgun spot will prove useful at Ramkat in W-S, NC, and some other wide/shallow rooms.   I've got a couple things coming up there so should be able to try it soon. 

The dual mid-side is fore and aft as Rolo 46 has proven with classical music over at Gearslutz.  I've run it once that way and didn't note any obvious problems. 
Center coincident shotgun to check against the dual mid pattern options, or mix with. 
Second coincident shotgun for PAS use, thinking to spot some extra vocal clarity, etc.  That clamp definitely needs a safety chain. 
AB omni outriggers at 30" spacing.  I've run them this width a couple of times.

I'd love to have a way to mount the DMS over/under as is typical, with the shotguns in between them, keeping the capsules as vertically close as possible, but I don't see how to achieve that easily.  This was as close as I could get it all without hardware or shocks touching each other. 

If it all turns out to be a giant phasey mess, well......

(https://live.staticflickr.com/65535/49097997232_338c818aba_c.jpg)

(https://live.staticflickr.com/65535/49097291713_bf8e4e838a_b.jpg)

(https://live.staticflickr.com/65535/49097802311_b0ed6a76cc_b.jpg)

(https://live.staticflickr.com/65535/49097291498_2e9271bb4a_b.jpg)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on November 21, 2019, 10:22:06 AM
If it all turns out to be a giant phasey mess, well......

Difficult to maintain tight coincidence with 4 mics.  That's a lot up there.

Looks like it might be possible to put both shotguns on top to get the stack tighter vertically by extending the rear vertical support upward, flipping the top forward-facing shotgun upside down, and moving the PAS shotgun from the bottom to just under the top shotgun, clamped to the rear vertical support.  PAS angle would then be adjusted by rotation of the clamp on the vertical support.  Depends on the ability to position the PAS shotgun coincidently that way.

If you can't get the PAS shotgun well-aligned that way, just flipping the top forward-facing one upside down should allow you to get that one in very close in above the DMS pair.

But this is all little more than armchair photo analysis.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on November 21, 2019, 11:18:17 AM
If it all turns out to be a giant phasey mess, well......

Difficult to maintain tight coincidence with 4 mics.  That's a lot up there.

Looks like it might be possible to put both shotguns on top to get the stack tighter vertically by extending the rear vertical support upward, flipping the top forward-facing shotgun upside down, and moving the PAS shotgun from the bottom to just under the top shotgun, clamped to the rear vertical support.  PAS angle would then be adjusted by rotation of the clamp on the vertical support.  Depends on the ability to position the PAS shotgun coincidently that way.

If you can't get the PAS shotgun well-aligned that way, just flipping the top forward-facing one upside down should allow you to get that one in very close in above the DMS pair.

But this is all little more than armchair photo analysis.

Yep, armchair analysis here too.  I will say there may be advantage in the vertical distance that's counterintuitive.  I've found multiple close mics in studio could be better or worse opposite of normal expectations.

One problem with the clamped extension is it's just a couple degrees off of straight, so there's another angle to fight in positioning.  Getting the shotgun capsule coincident is harder than expected, with a fight between available mount position/obstruction and mic position within the mount.  No one would be throwing a rig like this up in a hurry, this is really more the kind of thing I can get away with in an official capacity, starting at soundcheck. 

I realize I neglected to try mounting the angle gun off of a right angle stud adapter connected to the center stud....and that might require a short extender to get the mic bodies higher. 

A right angle mount for the DMS that allowed both to mount horizontally with front/rear running left/right and side running front/back orientation would collapse the height requirement substantially. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on November 21, 2019, 11:42:26 AM
I also find the coincident thing sometimes behaves oddly outside of a straight coincident stereo pair.  I've tried omnis coincident with supercards in a standard near-spaced stereo arrangement in an attempt to extend bass response a few times but that never worked right without low-passing the omnis (yeah I know that's the "right way" anyway), regardless of omni level, even though the mics were very closely coincident and theoretically shouldn't have had significant phase conflicts above the low-pass.

I've seen photos of a L/C/R arrangement which intentionally used a very large vertical spacing.  It was built upon a standard near-spaced 2-channel L/R pair with a center mic placed directly above it something like 2 meters  higher.  The intent was to have relatively close near-spaced coincidence for direct-arrival in the horizontal plane, combined with significant decorrelation for diffuse reverberant sound arriving from all directions.  No idea how well it worked though.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on November 21, 2019, 02:16:32 PM
Interesting, 2 meters is huge.  I've had problems at times.  OTOH, you might remember I did a MS thing with the side between a card and an omni, and found I could treat them as a single variable pattern mic.   MKH though, very well behaved in the first place, and much closer than my theory above.  I definitely plan to do more 8 and omni combos for picking pattern later. 

(https://live.staticflickr.com/4862/32475246938_b982763158_z.jpg)

I've run a pair of omni together a lot lately in studio world, so I could pick the preferred sound later.  In a couple cases I've run them 50/50 in the mix with no artifacts.  That's a KM131 with an MKH20, both ruler flat on paper, but very different sounding.  The Neumann is soft up top but has a great lower mid range quality, and the Sennheiser has more articulation in the treble and lower bass. 

(https://live.staticflickr.com/65535/47812810552_c473717516_z.jpg)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on November 21, 2019, 04:12:42 PM
I definitely plan to do more 8 and omni combos for picking pattern later.
^
This remains high on my list as a modification of the wide A-B omnis in an OMT setup to dial in variable front/back sensitivity. 

May prove useful for stereo mixes as well, but the primary motivation is better use of those channels as discrete surround feeds by providing control over how much forward direct sound is picked up by them.. I once determined I needed at least 6dB reduced forward sensitivity in the omnis when they were routed to the surround speakers in order to keep the front image from bleeding into the surrounds (and for that reason have considered rear-facing subcards in place of the omnis as a simpler if non-variable alternative).  If that works well enough I may be able to eliminate the seperate near-spaced rear-facing supercard pair, and keep the channel count the same.  [edit- although it works really well to route the near-spaced rear-facing supers to the rear surrounds and the omnis (or better, rear-facing subcards) the the side surrounds in a 7 ch surround playback arrangement..]

To do that I need to overcome the practical challenge of supporting the 8's and their cabling on the feather-light telescopic bar I use (again, rear-facing subcardioids may be the more practical answer).. and I'd need to pickup another sd 8 since I only have 2 on hand and don't want to give up the one used in the center MS pair.  Would be more easily doable in a few joints where there is a long railing and I can just clamp the 8's.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on November 21, 2019, 05:41:33 PM
Take 2.  Closer, easier, better.....in theory.  Could flip the Two MS mics position and get the center shotgun a bit closer. 

(https://live.staticflickr.com/65535/49101535818_598ece2ef8_b.jpg)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on December 04, 2019, 12:57:44 PM
Checked David Griesinger's website this morning, which I do a few times a year [http://www.davidgriesinger.com/] and found the portion quoted below in a recent post.  My bold emphasis on his assertion which I take as confirmation of an important aspect I hear and continued to pursue via OMT arrays-
 
"10/31/19 I have been so busy I have not had time to update this website with the new code for LOC, our measure that predicts from a binaural impulse response whether a particular seat will provide “Proximity”. The experiments shown in the paper for that talk showed that reflections that arrive up to 5ms after the direct sound augment the direct sound, and increase the likelihood of hearing proximity. But reflections that arrive after 7ms decrease proximity. I added a cross-fade window centered at 6ms in LOC to account for these perceptions."[snip]

Greisinger has been interested in identifying the auditory perception of what he calls "Proximity" and developing quantifiable measurements for it, in order to provide more useful acoustic tools for the design and optimization of acoustic performance spaces.  I've found one way OMT arrays differentiate themselves from more typical stereo recording microphone setups is that they are often able to provide a stronger perception of proximity as each pair is brought up in the mix.  Although my application is in some ways the inverse of what he is focused on, I see it as providing similar perceptual cues to the listener.  While DG is describing a perceptual attribute of the soundfield and how it varies at specific positions in a hall, and I am building microphone arrays partly intended to improve perceived sound quality when recording from a location that is somewhat more distant than would be desirable, I suspect OMT arrays may be leveraging the same perceptual attribute.  They may be in effect synthesizing proximity cues via the geometry of the microphone array itself.  For instance, the OMT8 array I'm using currently samples the soundfield across 7 positions in space within a 5-6 foot left-right horizontal-axis and about a 1-1/2" front-back axis.  That spacing correlates to a maximum time-of-arrival difference of 5 to 6ms for sound arriving from the sides.  Ignoring the rear-facing pair (intended to exclude front arrival sound), there are 5 sampling positions arrayed horizontally left-right which correspond to 3 stereo pairs contributing to front sound pickup: A center M/S pair, 5-6' spaced omni pair, and mid-spaced 90 degree angled supercardioid pair.  I am repeatedly struck by how muting of any one of those 3 pairs in the mix significantly reduces the perception of "proximity" and is one primary reason I've willingly if somewhat begrudgingly shifted from 6 to 8 channels.

I also see a possible parallel here with Tony Faulkner's 4 microphone phased array setup (not his older parallel 8's setup) and other "multiple microphones arranged in a line" techniques some tapers are using.
Title: Headphone equalization
Post by: Gutbucket on December 04, 2019, 01:22:25 PM
Also noted on this visit to David Griesinger website is increased focus on making his headphone equalization technique I've mentioned before more widely available (DGSonicFocus now mentioned prominently at the top of the homepage) via an application used to help equalize headphones to match the hearing response of the listener. It allows individuals to find the precise equalization for their headphones which matches the sound pressure they hear through the phones to the sound pressure from a flat-frequency loudspeaker positioned directly in front of them.  I've mentioned this here previously, requested the program and received it along with other information from him last year with the intent of starting a discussion about it here at TS, yet still haven't found the time to explore it myself, much less start a new thread dedicated to it.  I remain excited to try it as it very much falls in line with my thinking on what is important with respect to the problem of accurate headphone reproduction.

"Our apps use a simple loudness comparison test to find an individual’s frequency response at their eardrums, both from a free-field source at the front, and from headphones and earbuds. The app then provides the precise equalization needed to give the listener accurate timbre and frontal localization without head tracking.   The difference in image and timbre with our equalization is startling.

The apps also provide a time domain transaural mode that reproduces the sound of [personally equalized] headphones [over speakers] without individual equalization. It was developed to demonstrate our binaural recordings of concert halls at acoustics conferences world-wide. When reproduced this way the recordings are startlingly real. ..One visitor who had hearing aids asked if it would still work. I said take out the aids and try the app without them. He was ecstatic. 'I can mix again with this!'"

In a similar if more complex mulitchannel vein, the Smyth A16 Realizer (https://smyth-research.com/#OverviewA16)Kickstarter project  (https://www.kickstarter.com/projects/1959366850/realiser-a16-real-3d-audio-headphone-processor/description)finally reached completion a few months ago and is now shipping out to backers.  I'm something like backer number 325 of the original 330 or so from 3 years ago.  Word is they are shipping about 10 units out per week and are currently around number 120, so I'm hoping to receive one next spring perhaps.  Despite the long delay I've been looking forward to this ever since undergoing a personal HTRF calibration and demoing the original A8 unit at a CanJam headphone convention in 2008, and have gushed enough about that experience previously in these threads.

Although for it to work optimally as intended one must place miniature microphones in the ears and make a series of physical HTRF measurements of actual speakers placed in the intended positions around the listener in an actual listening room, this unit now also includes a simpler headphone equalization mode which appears to be based directly upon Griesinger's approach.  Some rather droll youtube videos of its operation, and less droll videos of demonstration reactions can be found here- https://www.youtube.com/channel/UC0yePwI_x1q8oACTVHpYxkw/videos
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on December 12, 2019, 05:53:15 AM
Thanks you all for great posts. I love to read it. I would like to ask one question. I have two old shotguns that I have never use. Gutbucket suggested that it should be possible to use shotguns in xy pointed at PA as the center mics. I am using xy cards in the center with spaced omnis now. Mostly I am M/S widening cards in post to fit it with spaced omnis. Has anyone experience of M/S widening of shotguns? Does it sounds good?

Maybe I can do something similar as EmRR. I can record six tracks, so I can add pair of cards and wide the center image by this pair. But I have no idea in which configuration should I setup the cards.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on December 12, 2019, 09:44:58 AM
I have two old shotguns that I have never use. Gutbucket suggested that it should be possible to use shotguns in xy pointed at PA as the center mics. I am using xy cards in the center with spaced omnis now. Mostly I am M/S widening cards in post to fit it with spaced omnis. Has anyone experience of M/S widening of shotguns? Does it sounds good?

Maybe I can do something similar as EmRR. I can record six tracks, so I can add pair of cards and wide the center image by this pair. But I have no idea in which configuration should I setup the cards.

I have not widened a shotgun pair before. 

If you haven't seen it, search member dsatz and shotgun, he has some good commentary about their usage and problems. 

I think the first experiment I would recommend would be for you to make an array with one coincident shotgun as part of your center, either aimed center or aimed at the closest stack (depends on the space you're recording) and see how that goes.  Since you are widening already maybe aimed dead center is best.  Experiment from there. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on December 12, 2019, 01:12:18 PM
Thank you EmRR, I will look for more commentary about shotguns. It is good idea to use xy with shotgun. I can compare mix with and without it. Couple years ago, I bought JVC mics (clone of Nak300) with cardiod caps and I got short shotgun caps too. I put shotguns in the drawer and forgot about it. But thanks to your and Gutbucket posts, I remembered them.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on December 12, 2019, 01:24:28 PM
How clean/direct/SBD-like is the pickup from your PAS X/Y cardioids in isolation?  The intent of switching from using cardioid directivity in that configuration to supercards, hypers, or shotguns is the pursuit of more clean/direct/SBD-like aspect from the center pair.  If you have enough of that already from your cardioids, or have direct SBD feed recorded, you needn't shift to using the shotgun(s).

DSatz raises excellent points about the problem of stereo recording using shotgun mics.  The switch from X/Y cardioids to supercardioids/hypercardioids is a generally straightforward one of increased directivity and reduced off-axis sensitivity.  The switch to shotguns is more complicated in that their off-axis misbehaviors come into play.  Non-uniform off-axis sensitivity affects things in a few ways: pickup of discernible off-axis sounds may sound odd, and any pattern-misbehavior which affects the stereo overlap region may affect imaging and tonal qualities of what the shotgun pair is intended to be focused on picking up.

While it's certainly true that shotguns aren't intended nor well-suited for typical stereo-pair mic'ing (other than MS shotguns), that never kept Grateful Dead section tapers from using them as PAS near-spaced pairs.. frequently in combination with a single omni.  The single omni not only extended low frequency response, but also served to audibly bury the lower-level off-axis misbehavior of the shotguns as it was not typically low-pass filtered.  The omni essentially covered up much of the shotgun problems as long as it could be used at a high enough level in the mix.  Too much would make the recording width collapse as all stereo width information was provided by the shotguns.

In a way, OMT takes that practicality-driven approach, inverts and optimizes it.  Combination with a wide-spaced omni pair (could be some other pattern) helps to bury the off-axis pickup of the shotguns in the mix in the same way, while using a single shotgun or coincident pair in the center reduces the phase-differences inherent to any near-spaced center microphone arrangement, especially the problematic phase behaviors of a near-spaced pair of shotguns.  The wide-spaced pair also contributes open and spacious sounding stereo room-reverberation/ambience/audience-reaction sound (highly decorrelated due to the wide spacing), rather than a single omni providing monophonic/100%-correlated pickup of all that stuff which is intended to be perceived as wide and enveloping rather than narrow and centered.  We then get phase and time-of arrival differences where that is beneficial, combined with cleaner, flatter level-difference stereo pickup where it is beneficial.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on December 12, 2019, 01:27:12 PM
I'm in agreement with EmRR about the best way to experiment with this.  Ideally do so by leaving your current setup using center PAS X/Y cardioids unchanged as a basis of comparison.  Add to that the PAS X/Y shotguns (cross them at the diagram locations at the back of the interference tubes) or a single center shotgun, as long as you have the ability to record those channels at the same time.

A single shotgun will give you some idea of how much increased isolation (clean/direct/SBD-like quality) an arrangement using shotguns can provide, while a PAS X/Y arrangement will be a better comparison for determining if direct replacement of the cardioid pair with an shotgun pair makes sense.  Of course if you have a fig-8 you could do MS with a single shotgun as an alternative to two in X/Y PAS.  However, I'm very interested in X/Y PAS shotguns as it represents a sort of maximum logical extension of the OMT for PA recording idea with regards to the center pair being optimized for role of direct sound pickup from an acoustically-distant* far-field location. 

If you then decide that a center X/Y PAS shotgun pair does what you want and wish to explore other uses for the cardioids as additional channels, we can discuss appropriate options for doing that.


*"Acoustically-distant" meaning further away than the direct/reverberant critical radius of the room, which is almost always considerably less than the distances from which tapers are recording, even when recording on-stage or from the stage-lip in smaller rooms.  Granted, it can be argued that the presence of directional PA reinforcement radically alters the normal critical distance relationship, which is one reason audience taper recording is an oddball endeavour to begin with compared to studio and non-PA amplified live performance recording.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on December 12, 2019, 01:37:20 PM
Note the white tape on my KMR81's, that's where the diaphragm sits in those.  There's some slots behind it too. 

MS with the KMR81 worked pretty well, I really can't fault it.  You can't get very wide with that if you are at distance, but you can get some representative stereo spread. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on December 12, 2019, 04:35:07 PM
The idea behind X/Y shotguns is to get maximal clean detail from the PA by keeping the shotguns directly on-axis with the PA stacks.  Then adjusting the stereo width of that with a MS ratio adjustment to blend it with the wide pair and provide the appropriate direct-sound imaging stereo-spread across the center.  In addition to maximizing pickup of PA direct sound in the center pair, a PAS X/Y arrangement should maximally capture any stereo difference information present through the PA, even if those stereo elements are only reverbs and effect returns rather than left/right stereo placement panning of sources - which is common even in many otherwise "mono" PA mixes.

EmRR's setup adding a single shotgun pointed at the nearest stack is intended to increase the capture of vocal clarity and on-axis PA detail, and uses that to bolster the forward-facing MS center pair which is providing stereo imaging across the center.  An X/Y PAS shotgun pair should better capture the direct-sound PA stereo elements.  It will be interesting to determine if a center X/Y PAS shotgun pair makes the original MS pair unneeded or overly redundant, such that those two channels could be repurposed or simply eliminated.

MS using a single shotgun Mid pointed directly forward attempts to maximally capture the direct sound from both PAs via one shotgun aimed between them.  The Side fig-8 "stereoizes" that with a microphone oriented perpendicular to the stage.  Rather than both microphones of the pair being pointed directly on-axis with the PA sources, neither is actually directly on-axis with the PA (even though the Mid is hopefully close to being so, unless your recording position is close making and the angles to the PA speakers wide). In some ways, this calls to mind discussions of the real-world practical difference between setting up a Blumlien crossed fig-8 arrangement as MS rather than XY.  Both arrangements are equivalent mathematically in terms of XY/MS matrix transformations, but it is argued that having the Mid microphone directly on-axis with a source directly in front of the microphone position represents a practical advantage for the MS arrangement using real world microphones.  Likewise its my hypothesis that it having two shotguns arranged so as to be directly on-axis with the PAs may be more advantageous than a single shotgun in MS.

But it needs to be sufficiently better that it makes the awkwardness of running a X/Y shotgun arrangement worthwhile!

Practicality reigns supreme.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on December 12, 2019, 04:49:48 PM
OK, this slightly simplified version is going out tomorrow.  More compact, less to fight.  This loses the 'dual' part of the MS, the rear channel.  Should get a board feed with it too.  Hopefully can share results. 

(https://live.staticflickr.com/65535/49210647827_3b016a669f_c.jpg)

(https://live.staticflickr.com/65535/49210421296_37c6a69426_c.jpg)

(https://live.staticflickr.com/65535/49210647527_037a6e52f7_c.jpg)

(https://live.staticflickr.com/65535/49210421001_af6dc016ef_c.jpg)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on December 12, 2019, 04:57:23 PM
Thank you very much for the explanation. I don't have a lot of practical experience. Sometimes happened, when I used xy cards and spaced omnis, that I had to use very little of omni in the final mix. I think it was because bad acoustic in the room. More clean and dry xy signal would be useful. It would allow me to add more omni in the mix.

On the other hand, when I was taping in great acoustic room, unfortunately that is not often, I didn't use much of xy. I have never experience big hole in the stereo omni track of the audience PA recording. So I am adding xy cards only to gently strengthen the center and bring more clarity.

You are right, the best will be to use two xy cards and two xy shotguns. It is the easiest how to compare. And I am curious how xy shotguns sound. Thank you for your help. I will prepare my staff. It will take me time to go to tape. But then I will let you know the results. Maybe the test will tell nothing, because the mics are cheap, for hobby.

Note the white tape on my KMR81's, that's where the diaphragm sits in those.  There's some slots behind it too. 

Yes, I will check where is the capsule in the tube. I don't even know if the shotguns work, I've never tried them. Must be nice to use KMR81 with fig 8 for the center in OMT. Your picture looks great. I am looking forward for your comments about the recording. I like your snake cable too. I saw your posts about it. I should do something similar. It has to make the setup easier.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on December 12, 2019, 05:53:53 PM
OK, this slightly simplified version is going out tomorrow.  More compact, less to fight.  This loses the 'dual' part of the MS, the rear channel.

Cool. Have fun with it.

I'd love to try an alternate version of that using the same mics, but with the two shotguns in X/Y PAS and the Mid of the MS pair facing rearward. 

..with three things in mind:
First, it's a test of the X/Y PAS shotgun thing for all the reasons mentioned above.
Second, it retains ambient/room/audience rear facing pickup in an overall arrangement of six channels in total.  The presence of which may make elimination of the forward facing MS pair more palatable.
And third, it retains the fig-8 Side mic.  I find that channel adds something compelling even when I don't or can't do a proper MS>LR conversion of the center pair (using the Zoom F8 for direct playback, as we've discussed elsewhere with regards to that F8 monitoring quirk) and simply bring up some of it in the OMT mix without any polarity inversion to the right channel.  It's part glue, part tonal.  Although that be more attributable to my particular setup using the 5 near-spaced miniature DPA supercards in the middle.


Thank you very much for the explanation. I don't have a lot of practical experience. Sometimes happened, when I used xy cards and spaced omnis, that I had to use very little of omni in the final mix. I think it was because bad acoustic in the room. More clean and dry xy signal would be useful. It would allow me to add more omni in the mix.

On the other hand, when I was taping in great acoustic room, unfortunately that is not often, I didn't use much of xy.

Makes sense, and is perfectly okay.  That you arrived at such a different balance between the two in different scenarios can be interpreted as exercising the powerful flexibility the arrangement provides.

Quote
I have never experience big hole in the stereo omni track of the audience PA recording.

Two things here:
I realize that it may not be practical to do so, but try spacing them further apart if you are able to.  If you do get a detectable center in the middle, the X/Y center pair will fill it, while the wider spacing will let the omnis do the wide-omni thing even better and any detectable hole arguably allows the X/Y pair to do its center-thing better in combination. 

This is one of the things that makes taper recording of PAs an oddity in the recording world.  Even huge 30 to 50 foot omni spacings can sometimes work.  Even though the stereo distribution of non-PA sounds are likely to pull strongly into either speaker with a big hole in the middle, monophonic PA content will be centered and not have a hole as long as the distance from the PA speakers on each side to the microphone location on each side is the same (identical content in both sides of the PA remains phase correlated at both microphones), while stereo pickup of any differential stereo stuff thru the PA such as stereo verbs, effects, maybe drum panning, is maximized using time-of-arrival differences from the widely spaced omnis (rather than via directionality of X/Y shotguns).  Truly diffuse non-direct sound such as venue reverberance and non-specific audience reaction is be completely decorrelated between channels to even the lowest frequencies due to the very large distance between microphones, making those recordings sound really big, open, and enveloping.

Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on December 16, 2019, 03:54:59 PM
6 channel rig worked fine.  Not as much difference in the two shotguns as I'd hoped, but definitely some.  Need more snare, the center.  Need more vocals/horns, the PAS.  I can turn on both mids and the PAS with no obvious combing/phasing problems, so that's great.  Just starting to check it out. 

At least one startled person emitted a 'GODD@^#M!!' when they noticed the rig as they walked by, so that was worth it alone. 

(https://live.staticflickr.com/65535/49230066012_6ce706625d_c.jpg)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on December 16, 2019, 05:17:04 PM
Heh, heh. Nice totem pole!

Sounds encouraging.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on December 17, 2019, 07:04:00 PM
6 channel rig worked fine.   Need more vocals/horns, the PAS.  I can turn on both mids and the PAS with no obvious combing/phasing problems, so that's great.

OK, one suspicion confirmed.  The angled coincident PAS when panned center still sounds like it's pointed at the angle, in other words the center image shifts in the pointed direction.  It can be offset by panning the other direction.  Mostly.  Only really obvious if you listen only to it and the side mic.  Slightly obvious when mixed with the other mid mic. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: rocksuitcase on December 17, 2019, 07:11:07 PM
Looking Good EmRR!
I can add to GB's thoughts on widely spaced omnis. The few times we have been able to go 10 feet or wider have resulted in very smooth, buttery omni tonality. twice was in large OTS' where we shared/clamped to someone else's stand 10 or so feet apart from our stand and only once we had three stands at a gig where we had a lot of leeway with the soundcrew and the omnis were about 12 feet apart. My opinion is as GB posits: spacing the omnis as wide as possible, with the exception of not being outside PA stacks can result in high quality decorrelated tonality and overall yumminess (technical term!)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on December 18, 2019, 12:21:51 AM
Thanks!   I gotta try wider omni soon.  In this particular room AB60-70ish mixes well with the coincident set, maybe because it’s a shallow space.  I can see wider being definitely cool with greater distance.  Need to try it in this room for comparison. 

I tried applying the crossover theory I mentioned earlier, then modified it.  I didn’t really like tossing the treble from the AB set, and lowered the HPF cutoff on the side signal of the coincident down to around 800.  Then changed it from a HPF to a low cut shelf with the same initial slope, max cut of -18.  I preferred the way the bass blended across the stereo field with the AB. At least in this case. 

The AB is currently -12 relative to the MS.  Adds a bass width that matched the treble info in the coincident set.

The shotguns are EQ’d with a low shelf cut to focus upper mid intelligibility and set -9.

This room has problems with vocal intelligibility in recordings, not as obvious to the ear.  I tried EQ’ing the board feed to be mainly upper mid vocal range and put enough in so it’s a slight improvement, lower than becomes obvious. 

Maybe laying out thought process on this will help someone else. Anyway, digging the experiments. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: prepschoolalumniblues on December 18, 2019, 12:01:08 PM
I was reading an old thread on spaced omnis with center card (https://taperssection.com/index.php?topic=163840.0) and was curious if anybody has been trying this three-mic configuration out lately. I'm thinking about trying this out with a pair of Line Audio OM1s (omnis) and a single center CM4 (somewhere between a subcardioid and cardioid) into the three-channel MixPre-3.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on December 18, 2019, 12:30:29 PM
I was reading an old thread on spaced omnis with center card (https://taperssection.com/index.php?topic=163840.0) and was curious if anybody has been trying this three-mic configuration out lately. I'm thinking about trying this out with a pair of Line Audio OM1s (omnis) and a single center CM4 (somewhere between a subcardioid and cardioid) into the three-channel MixPre-3.

Definitely try it!

Edit: You might also want to check out this thread http://taperssection.com/index.php?topic=182566.0 and this one http://taperssection.com/index.php?topic=182579.0
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: prepschoolalumniblues on December 18, 2019, 12:50:51 PM
Thanks! I’ll add that the reason I’m thinking about this is because the CM4 doesn’t have quite as much bass as I’d like (especially from far away) so bass extension would be one of the main goals here (as opposed to running just a pair of CM4s).
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on December 18, 2019, 01:19:55 PM
Thanks! I’ll add that the reason I’m thinking about this is because the CM4 doesn’t have quite as much bass as I’d like (especially from far away) so bass extension would be one of the main goals here (as opposed to running just a pair of CM4s).

Interesting.  I never found the bass lacking in my CM3s, but it would make sense that the CM4s have less bass because they're closer to a normal cardioid pattern.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on December 18, 2019, 02:05:02 PM
I was reading an old thread on spaced omnis with center card (https://taperssection.com/index.php?topic=163840.0) and was curious if anybody has been trying this three-mic configuration out lately. I'm thinking about trying this out with a pair of Line Audio OM1s (omnis) and a single center CM4 (somewhere between a subcardioid and cardioid) into the three-channel MixPre-3.

Yes try it!  Really not terribly different in purpose than my complex rig.  Think of all my crap in the middle as one sound source, just built out from mono with options.  No reason not to stick up cm4 middle pair with cm3 flankers either if you have the record channels. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on December 18, 2019, 02:47:51 PM
I was reading an old thread on spaced omnis with center card (https://taperssection.com/index.php?topic=163840.0) and was curious if anybody has been trying this three-mic configuration out lately. I'm thinking about trying this out with a pair of Line Audio OM1s (omnis) and a single center CM4 (somewhere between a subcardioid and cardioid) into the three-channel MixPre-3.

Yes.  It may help to conceptually think of this as spaced omnis +.   In other words, mostly spaced AB omnis plus additional help from the mic in the center. 

The thread heathen linked above is a good read on that, being more concise than these OMT threads which also cover it.  I just added a comment and edited my previous last post there.


Things to keep in mind:
The most appropriate choice of center pattern in such a 3-microphone setup boils down to the question: In what ways should center microphone pickup differ from AB pickup? ..which relates to at least two different, sometimes contradictory aspects.  The center microphone mostly contributes forward presence and direct focus, yet needs to do that in such a way that it blends in seamlessly.

If you can't space the omnis much, a more directional center microphone can help to avoid problematic interaction between the omnis and center (there is no available spatial hole to fill). In this case the center microphone is primarily providing increased direct-sound pickup and clarity which gets overlaid on the already seamless spatial stereo "bed" provided by the omnis.

As AB-omni spacing is increased it can help to shift to a wider pickup pattern for a single center mic.  That helps blend the center channel contribution seamlessly into the stereo mix so that when brought up to a desirable level it is not perceived as being separate from what the omnis are providing  - separate both in terms of Left/Center/Right energy-balance (hole-in-the-middleness) and in terms of timbre.  You don't want the contribution from the center mic to be perceived as a sort of separate narrow pool of sound tightly centered the middle of the playback image (more likely when the timbre in that channel differs greatly from that of the omnis) because if that happens you can't raise the level of the center channel enough in the mix to make a useful contribution without calling too much attention to it.  In that case we need more overlap / interaction between the center and AB omnis rather than less.

Yet at the same time, use of a more directional center microphone is desirable to achieve enhanced clarity and presence of the direct-sound pickup.  This is why going to a coincident stereo pair in the center works so well.  We can get both that clarity as well as a bit of increased spatial width in the center which helps it blends in with the omnis.  Plus we get the ability to adjust that center width in the mix.  A single center mic works too, you just need to home in on the optimal pattern/spacing arrangement with a bit less flexibility afterwards in the mixing stage.

To really get a good handle on what's going on, try it both ways- A pair of spaced OM1s with a single center OM4, versus a pair of OM4s with a center OM1.  Without any EQ filtering applied there will be limits to how narrow and how wide the pair should be spaced for all three to work best in combination, but either way should have the pair spaced somewhat wider than if that pair was in use alone without the center microphone channel.

Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on December 18, 2019, 02:52:24 PM
Thanks!   I gotta try wider omni soon.  In this particular room AB60-70ish mixes well with the coincident set, maybe because it’s a shallow space.  I can see wider being definitely cool with greater distance.  Need to try it in this room for comparison. 

I tried applying the crossover theory I mentioned earlier, then modified it.  I didn’t really like tossing the treble from the AB set, and [snip]...
Maybe laying out thought process on this will help someone else. Anyway, digging the experiments.

EmRR, thanks for relating what you are doing in mixing with regards to crossovers, levels & EQs.

I also like the high-frequency contribution from the AB omnis and find it works nicely in a 2ch mix as long as there is sufficient AB width.  It provides attractive "air".  I speculate that a LPF on the AB pair (possibly as the lower half of a crossover arrangement with the center MS pair) may be most useful where one cannot achieve sufficient AB spacing - avoiding less desirable comb filtering interactions arising from a relative near-spacing.  Further increased AB width makes this HF aspect work even better in addition to making the LF aspects work better.. presumably for similar reasons, although in the longer-wavelength LF range that will be in the mode of phase interaction, while in the HF range the interaction will be in the time-of-arrival mode (since the same spacing represents multiple-wavelengths in that higher frequency range).

I might have additional comments on what you've posted about this and will go back to it when I have a chance.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on December 22, 2019, 11:39:48 PM
[snip]
The AB is currently -12 relative to the MS.  Adds a bass width that matched the treble info in the coincident set.

The shotguns are EQ’d with a low shelf cut to focus upper mid intelligibility and set -9. [snip]

The shotguns are seductively dangerous.  In the end I took them down to -12 relative to the main M of the MS.  I decided they were adding too much of an odd 'in yer face-ness' at some frequencies that would really pop out on certain voices and horns, not on other things at all.  Slighty lower seems to give a more desirable amount of that without distorting the overall perspective. 

Also decided I had the AB contribution sounding wider than the treble info in the MS, which doesn't add any useful info in this room, just more side wall bounce and audience noise. Seductively dangerous again, exciting at first but didn't wear well with repeated listenings.   Took it down to -18, definitely still there (surprising), nice filling out of the bottom without being bloated or artificially wide.   Big resonant room bloat around 200Hz too, even mixed that low I took a little of that range down to clean up some mud. 

Some of this one is a battle with an OK but not great PA mix, large band with horns and multiple singers, varying mic techniques and horn volume, acoustic bass notes with strong resonances, etc.  A lot of the voices had too much proximity effect so were bass heavy with not articulation, but a couple singers stayed of the mic and sang with a lot of volume, so they sound thin in comparison.  A couple of horns were so loud they were hardly in the mix, others were louder than voices in the PA. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on December 27, 2019, 02:50:00 PM
Trying a horizontal only native B format surround array in the middle of spaced omnis with Emma Gibbs Band at Ramkat tomorrow.  Had to cut down the Shapeways mount to get spacing for the omni mic.

(https://live.staticflickr.com/65535/49282494258_d5410285a7_c.jpg)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on December 27, 2019, 05:50:27 PM
Hmm, because some of the flat portion of the mount needed to be removed to fit over the cylindrical portion of the mic body close to the capsule end?  I couldn't figure out why from the photo above until I went back and looked at the shot you posted of same mount without the omni here- https://taperssection.com/index.php?topic=191953.msg2315073#msg2315073
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on December 27, 2019, 05:53:58 PM
Yeah, not much space available between the mics. 

Recorded a rehearsal with this setup in a small space today, checking out the new RODE Soundfield processing plug, more flexibility than the older Soundfield plugin.  Adds a shotgun mode.

Also:   that swing arm mount with the clamp I used for the PAS shotgun wroks great here for the omni, it's clamped to the mic stand. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on December 27, 2019, 07:27:36 PM
checking out the new RODE Soundfield processing plug, more flexibility than the older Soundfield plugin.  Adds a shotgun mode.

I wonder if that is based on the 1st order ambisonic "focus" variable which essentially modifies the omni W component to increase bias in a certain direction (something like that, not sure about the technical aspects) or some other signal manipulation.  The implementation of "focus" in VVMic is seductive with my TetraMic recordings in providing increased direct clarity, yet is easy to heavy-hand.  Just a touch seemed to work best without affecting other aspects negatively.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on December 27, 2019, 11:28:26 PM
checking out the new RODE Soundfield processing plug  Adds a shotgun mode.

I wonder if that is based on the 1st order ambisonic "focus" variable which essentially modifies the omni W component to increase bias in a certain direction (something like that, not sure about the technical aspects) or some other signal manipulation

Not sure, I haven't spotted info beyond the website.   The pattern control has two settings, one runs omni to figure 8, the other runs cardioid to what looks like a second order oblong shape with no rear pickup. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on December 29, 2019, 04:31:09 PM
Was hoping to use an extension bar to get the AB wider, but discovered I'd have no place to clamp the B format omni.  Probably could have figured it out, but had no time to think about it. 

(https://live.staticflickr.com/65535/49294699833_5b85cca0d9_c.jpg)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: noahbickart on December 30, 2019, 08:38:51 AM
Here's last night's Phish show with mk41v pair XY PAS + mk3 (omni) at 50cm AB

mp3: https://drive.google.com/open?id=1fSLds_eVpStuZxW9uLoaqH3G8YF3-Kck
24 bit: http://bt.etree.org/details.php?torrentId=608098
16 bit: http://bt.etree.org/details.php?torrentId=608096
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on December 31, 2019, 11:05:27 AM
Thanks Noah!  Will be interesting to compare with rocksuitcase and kindms's OMT6 pull from the same night (I think).
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kindms on December 31, 2019, 11:48:51 AM
Thanks Noah!  Will be interesting to compare with rocksuitcase and kindms's OMT6 pull from the same night (I think).

correct. we were about 7-10 ft behind Noah maybe a little less than that.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on December 31, 2019, 01:28:14 PM
Gotcha, thx.  Double posting my comment made in the rigpics thread earlier this morning over here to continue the discussion..

On the OMT mics: we ran the 6 channel OMT into a DR680 using kindms 426 in hypercard XY this night 65' as the center. then the akg ck22 omnis spread 120cm and akg ck61's aimed at 45'/PAS about 60cm apart equidistant from the middle. The ck22s went into a Grace V2, the c426 into a Grace V3, and the ck61's went used the 680's pre-amp.

Is this the first you guys have tried this particular 6ch OMT combination?  I suspect you are really going to like what the part I've bolded above adds to the coincident center and wide omnis.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on January 07, 2020, 04:14:23 PM
https://taperssection.com/index.php?topic=191953.msg2318816#msg2318816 (https://taperssection.com/index.php?topic=191953.msg2318816#msg2318816)

The band was rehearsing at my studio before the gig, so I dropped the 3 channel horizontal B format array in the middle of them to experiment.  They were all facing each other in a circle. 

I settled on a 'best' stereo result, then enabled 3 more virtual mono patterns to get more mandolin, balance the kick drum out with the bass, and more of one of two electric guitars.  Those three have pretty heavy EQ (band-passed or LPF) and one is polarity reversed.    So many options you are easily confused. 

I can't get everything out of it, but pretty close.  Vocals were floor wedges only, and while there, are sorta equally in everything as a darker sounding background sound, can't really be pulled out. 


The gig had AB omni outriggers, and unfortunately, one of those reunion audiences that talked loudly the entire show.  I multi-tracked everything so can build a clean mix.   I'd have liked to use more room sound for realism, but not when it's audience talking!  Settling on a ambisonic pattern close to PAS short shotguns to minimize the crowd while getting some room feel.  I suppose if it was full ambisonic I'd try pointing it up at the ceiling for reverb bounce away from the crowd. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on January 10, 2020, 10:51:55 AM
^ That's cool.  I'd originally planned to hang the TetraMic from the center of a 10' x10' pop-up canopy for circled up campsite jams at music fests, but never actually got around to doing it.  However, and somewhat similar to what you mention doing, for a few on-stage/stage-lip recordings I dialed up a couple additional virtual pattern channels to better balance things in addition to the primary stereo-pair output.  It made me quite aware of the limits of first order pattern tightness, but I didn't have the ability to synthesize shotgun-like greater than 1st order hyper directionality.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on January 10, 2020, 10:54:02 AM
I've been enjoying listening to the recent MSG Phish recordings during some late night work sessions this week, thanks guys!
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on January 10, 2020, 11:43:07 AM
I was checking Don Keele's papers on his website to see what he's been up to recently..
https://www.keele-omholt-technologies.com/papers.php (https://www.keele-omholt-technologies.com/papers.php)

..and had to grin when I looked through this one from 2016- Use of Ground-Plane Constant Beamwidth Transducer (CBT) Loudspeaker Line Arrays for Sound Reinforcement
https://www.keele-omholt-technologies.com/papers/Keele-CBT-Paper-11-Sept.-2016-Use-of-Ground-Plane-CBT-Arrays-for-Sound-Reinforcement.pdf (https://www.keele-omholt-technologies.com/papers/Keele-CBT-Paper-11-Sept.-2016-Use-of-Ground-Plane-CBT-Arrays-for-Sound-Reinforcement.pdf)

In which he suggests using CBT arrays behind the performers in a way strikingly similar to the Dead's classic Wall of Sound. I read through but found no mention of the Dead's pioneering PA work, though it seemed tantalizingly close when he mentioned how it could compensate for poor array coverage problems of a small concert he came across in San Francisco's Presidio in 2009 and includes a photo of the clustered point-source PA setup with KFOG banner across the back of the stage. 

Granted CBT is different in important ways from traditional linear arrays such as the WOS and similar related (ie non-DSP managed) smaller-scale Bose type line arrays. It stems from declassified sonar beamforming advances made in the late 1970s, and definitely qualifies as an oddball speaker technique.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on January 27, 2020, 12:46:56 PM
I was listening to the interesting Grateful Dead matrix . The matrix is from 3 sources, sbd + two aud. Little disadvantage of the matrix is a less clarity. But it has great depth, the third dimension. I love how it is sounding. It remains me OMT with back pointed mics. We are trying to achieve the same effect.
https://archive.org/details/gd1991-06-09.128299.mtx.dusborne.flac16 (https://archive.org/details/gd1991-06-09.128299.mtx.dusborne.flac16)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on January 27, 2020, 12:59:10 PM
I recorded a show on Friday (Mike Dillon Band) with XY Sennheiser e614s (supercards) and wide-spaced omnis (DPA 4061s).  The Sennheisers picked up more direct sound and less of the crowd, so I decided to primarily use those.  The DPAs definitely picked up more of the bass, though, so I ended up doing a pretty drastic LPF before mixing in the DPAs.  Once they were all mixed together, the bass seems to have more stereo spread than the rest of the frequency range (the LPF was high enough that some of the sound can be localized).  I'm hoping  to have it all ready to share soonish.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: rocksuitcase on January 27, 2020, 03:57:03 PM
I recorded a show on Friday (Mike Dillon Band) with XY Sennheiser e614s (supercards) and wide-spaced omnis (DPA 4061s).  The Sennheisers picked up more direct sound and less of the crowd, so I decided to primarily use those.  The DPAs definitely picked up more of the bass, though, so I ended up doing a pretty drastic LPF before mixing in the DPAs.  Once they were all mixed together, the bass seems to have more stereo spread than the rest of the frequency range (the LPF was high enough that some of the sound can be localized).  I'm hoping  to have it all ready to share soonish.
\Oooh, can;t wait. Mike Dillon rocks! and any members of his band are typically talented as hell.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on January 27, 2020, 05:51:14 PM
I recorded a show on Friday (Mike Dillon Band) with XY Sennheiser e614s (supercards) and wide-spaced omnis (DPA 4061s).  The Sennheisers picked up more direct sound and less of the crowd, so I decided to primarily use those.  The DPAs definitely picked up more of the bass, though, so I ended up doing a pretty drastic LPF before mixing in the DPAs.  Once they were all mixed together, the bass seems to have more stereo spread than the rest of the frequency range (the LPF was high enough that some of the sound can be localized).  I'm hoping  to have it all ready to share soonish.
\Oooh, can;t wait. Mike Dillon rocks! and any members of his band are typically talented as hell.

He had Norwood Fisher from Fishbone on bass.  Unfortunately the sbd feed was a big fail and the mix in the room wasn't fantastic, but hey them's the breaks.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on January 27, 2020, 08:50:48 PM
http://taperssection.com/index.php?topic=193311.0

I'm curious what you guys think of this.  I'll reserve my own opinions for the time being.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on February 07, 2020, 07:26:22 PM
http://taperssection.com/index.php?topic=193311.0

I'm curious what you guys think of this.  I'll reserve my own opinions for the time being.

No major complaints, seems like a pretty clear room representation. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on February 07, 2020, 07:31:27 PM
Trying the same horizontal Ambisonic with AB again, AB120 this time (wider), and an added coincident shotgun.  Sure glad I played with LEGO's as a kid.

(https://live.staticflickr.com/65535/49503831912_270f42a4be_c.jpg)

(https://live.staticflickr.com/65535/49503105048_0bb540dc75_c.jpg)

(https://live.staticflickr.com/65535/49503105473_cd4712567b_c.jpg)

(https://live.staticflickr.com/65535/49513537073_43a46f2b09_c.jpg)

(https://live.staticflickr.com/65535/49514274737_a45ee2beab_c.jpg)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on February 10, 2020, 11:55:51 AM
http://taperssection.com/index.php?topic=193311.0

I'm curious what you guys think of this.  I'll reserve my own opinions for the time being.

Sounds to me like a clear representation of a somewhat difficult room / PA mix, with early reflection energy cluttering direct sound first arrival.   In assessing that I sort of compare the portrayal of audience generated sounds dispersed throughout the room and the decay of the room sound itself, in contrast with the sound from the band through the PA.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on February 10, 2020, 12:04:56 PM
Sure glad I played with LEGO's as a kid.

(https://live.staticflickr.com/65535/49503105473_cd4712567b_c.jpg)

Totally LEGO-licious!  Chuckling at the hall-of-fame-grade assembly complexity displayed in the above photo.

Cool that you were able to manage the wider spread.  Do you feel that aspect translates in a significantly differently way in the mix?

Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on February 11, 2020, 03:25:23 PM
Cool that you were able to manage the wider spread.  Do you feel that aspect translates in a significantly differently way in the mix?

I can't tell that it does in this case.  Fairly shallow wide room with long decay time, more ambient than it should be for a loud show.  Stand position is offset from center, so the most significant thing I notice is the change in lopsidedness related to the closer PA stack, which isn't a big deal in the overall mix, the AB being significantly down in the mix for reasonable bass contribution.  In this case I am low-passing the AB at 6dB/oct at 3kHz.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on February 13, 2020, 04:06:30 PM
OK, comparing the standard Manfrotto bar width to this, this sounds definitely wider, maybe too wide for my taste in this room.  Sounds good on speakers, really wide on headphones.  I may make a V shape with AB back some to get a width in between next time.   

The Ambisonic array winds up 71º angle with the most shotgun like pattern available in the Rode Soundfield plug.  The KMR81 is also in the middle, down 12-15dB, and band-passed to lose the hard treble sparkle and bottom.  Lots of early reflections to fight in this room.  AB is down -15 relative to the ambisonic mic levels before they hit the encoder.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on February 13, 2020, 07:51:04 PM
Sounds good on speakers, really wide on headphones.  I may make a V shape with AB back some to get a width in between next time.

Over the years I think I've sort of trained myself to target "slightly overwide, yet acceptably so" when assessing using headphones with speakers in mind.. sort of shooting to split the difference in an attempt to satisfy both.  Maybe I've now internalized that as sounding "correct".

I probably posted here not that long ago about recently using a forward angled 'V' AB config, due to the constraint of how I had the near-spaced L/R supercard pair mounted to the telescopic antenna AB arms in my rig.  I'd originally set it up so those supercards were at a near +/- 90 degree arrangement (ala Theil's OCT L/C/R) whenever I used the BAS Shure windscreens on them, even though I arranged it so that I could angle them slightly more forward than that even with the arms in-line pointing straight out to the sides. After deciding that I wanted to modify their angles to +/- 45 degrees even when recording outdoors, I achieved that by temporarily by angling both telescopic arms forward enough to get the L/R supercards to +/-45 degrees. That shifted them slightly forward somewhat in relation to the center M/S pair and pushed the omnis at the ends of the arms much farther forward.  Although those changes weren't desirable (I prefer them in-line, and would rather push the omnis backwards if necessary), I didn't find significant negative impact from dong so, and significantly preferred the more forward angled L/R supercard pair.

A few weeks ago I finally re-worked the way the BAS Shures are supported on the arms before recording at a local outdoor amphitheater so that they now achieve +/-45 degrees with the arms straight out to the sides.  I didn't get good photos of that but I may record at another local amphitheater this weekend and if so I'll be sure to snap a few.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on February 17, 2020, 11:48:45 AM
Question for the OMT experts.  I'm finally getting around to working on my JRAD Red Rocks recording from last summer.  I ran DPA 4061s spread as wide as I could...at least 15 feet I'd say.  Going into the show I was planning on sticking with just that but for the hell of it I took a patch from Todd R's MG M200 rig that was set up in the center of the "section" (and thus about the center of my DPAs).  I figured I could use those sweet sweet MGs to fill in the center of the DPAs if needed.

When I started mixing them together, though, the stereo image got weird at times.  It's most noticeable on a guitar solo, where it will sound like it starts to come from one side then shifts to the other side (left/right in the stereo image, that is).  I kept track of which mics were in which channel so I'm pretty confident I don't have the L/R channels mixed up.  I did try swapping the channels of one set of mics and that seriously messed things up so I don't think that's the issue.  Todd's mics were in a near-spaced configuration...I think it was approximately DIN.

Does anyone have an idea about what could be going on here?
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: rocksuitcase on February 17, 2020, 01:13:49 PM
Question for the OMT experts.  I'm finally getting around to working on my JRAD Red Rocks recording from last summer.  I ran DPA 4061s spread as wide as I could...at least 15 feet I'd say.  Going into the show I was planning on sticking with just that but for the hell of it I took a patch from Todd R's MG M200 rig that was set up in the center of the "section" (and thus about the center of my DPAs).  I figured I could use those sweet sweet MGs to fill in the center of the DPAs if needed.

When I started mixing them together, though, the stereo image got weird at times.  It's most noticeable on a guitar solo, where it will sound like it starts to come from one side then shifts to the other side (left/right in the stereo image, that is).  I kept track of which mics were in which channel so I'm pretty confident I don't have the L/R channels mixed up.  I did try swapping the channels of one set of mics and that seriously messed things up so I don't think that's the issue.  Todd's mics were in a near-spaced configuration...I think it was approximately DIN.

Does anyone have an idea about what could be going on here?
Not sure what is going on without listening, BUT, in your case I have done a gutbucket technique of "monoing" the coincident stereo pair for centered imaging but leaving the omnis to provide the stereo cues.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on February 17, 2020, 01:36:54 PM
I might play with MS processing on the center pair to see if it gives any clues.  The other thing would be to try moving the center and AB pairs apart by 6dB, see if it images better with one more predominate. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on February 17, 2020, 05:43:26 PM
It's most noticeable on a guitar solo, where it will sound like it starts to come from one side then shifts to the other side (left/right in the stereo image, that is).

To establish a starting point for the discussion, does each source (wide DPAs, near-spaced MGs) behave the same or differently with regards to this particular guitar panning phenomenon when listened to in isolation?
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on February 17, 2020, 06:36:50 PM
Didn't end up recording this weekend, but snapped a few photos in the parking lot yesterday while starting rework on the rig, currently in process.  Latest changes are the repositioned L/R big Shure windscreens to angle that pair ~ +/-45° when the main arms are +/-90° in-line with each other.  Note the holes in the front of them, through which the antenna arms formerly passed, angling that pair ~ +/-75-80°.

Other changes are the addition of a gaff-wrapped bent-coat-hanger support-wire to help support the rear-facing pair (similar to what I've long used to help support the main arms), and the addition of the hinged AT mic-clip for the center M/S pair, which was rigidly mounted previously, making for easy vertical angle adjustment which helps point up at PA somewhat and reduce the pickup of audience in the center as well as making for more compact rig stowage without disassembly with the mic folded down so as to be nestled in with and parallel to the others.

You may note the extra, currently unused stubby XLR up there, which I'll probably eliminate. 

I'm thinking of adding a flexible vibration isolation assembly between the center hub and stud which mounts to the stand, extension, or clamp, shock-isolating the entire assembly.  I'll need to determine the right stiffness for that to work effectively: flexible enough to reduce transmission of noise through the the stand or clamp, yet stiff enough to not wobble excessively.  They exist to isolate entire Decca trees and the like, but if I rework the center hub to which the antennas attach I may build something which incorporates some thick Sorbathane I have on hand.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on February 17, 2020, 08:49:26 PM
Looks great
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: rocksuitcase on February 19, 2020, 02:30:10 AM
Nice looking changes. I especially like how it all folds up and looks like a gang of Big Ass Shures!  8)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on February 19, 2020, 03:18:26 PM
Thanks. With all five Big Ass Shures in place and without the center mic being able to fold down I couldn't fully close the 30" x ~7" diameter padded bag I had been using, and was just toting it around half zipped.   The rig fit nicely in that bag using the smaller indoor-only windscreens everywhere except the center M/S pair, but I decided its too much hassle and stress on the wiring and windscreens to switch regularly back and forth to the BAS, so I decided to leave the BAS on basically all the time unless I'm in a situation where a smaller visual impact is especially important.  I searched to find a more appropriate sized bag and ended up with the Neewer photo gear bag.  Overall its slightly larger than necessary and than I'd prefer, but of everything I came across this was closest to the dimensions required. The big stand lays across the top of the bag and secures in place with two integral clip/cinch straps.  If not using the big stand I can fit clamps, telescopic extension bar and folding tripod foot in the main compartment, which can be somewhat compartmentalized using 3 provided velcro-placeable dividers.

The F8, TallentCell battery and peripheral recording stuff fits in the padded front pocket and I plan to cut a pass through into the main compartment for the cable snake.
 
The DPAs all use Naiant PFAs plugged directly into the recorder except the center supercard which uses a DPA phantom adapter which up to this point I had mounted aloft directly behind the mic at the hub.  I've had it set up that way ever since I transitioned from a single rear-facing mic to a pair.  I'm now rearranging things to move the DPA adapter down to the recorder along with the PFAs by using a CD-Int female-microdot>male-microdot extension cable, which explains the extra XLR up top which is now unused.. thinking I may leave it up there to facilitate experimentation with alternate center microphones.

The Naiant PFAs terminate in pairs to mini-xlr plugs to which the snake to the mics attach.  The strips of gaff-tape on those and on the PFAs themselves identify which is which, by feel in the dark if necessary.

Title: Re: Oddball microphone technique (OMT) - part 3
Post by: prepschoolalumniblues on February 22, 2020, 10:26:07 PM
I have a MixPre-3 but have only used it with a stereo pair. This week, I picked up a Manfrotto 154 triple mic bar (65cm wide, or just over 2 feet) and a handy-dandy custom three-channel XLR cable from Ted, so I’m really excited to try out a new approach.

Here’s what I’m currently thinking: I’d like to try wide-spaced subcardioids (using the full width of the bar, 2 feet) with a hyper in the center. I typically record amplified music indoors in small, not-great-sounding, weirdly-shaped rooms. My thinking is that by using subcards I’m taking the more “standard” OMT approach of spaced omnis and making it slightly more directional to compensate for a limited footprint (I would have a hard time going beyond 2 feet wide in the rooms I record in) and the room acoustics. The hyper would provide center clarity and help avoid any perceived hole in the middle.

Am I off-track here? Any thoughts on angling the subcards versus having them point straight ahead like an A-B omni pair? (Should I just go with an omni pair?)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on February 24, 2020, 12:13:11 PM
I'd give it a go initially with the supercardioid in the center facing directly forward and the spaced-subcardioid pair angled ~ +/-45 degrees.. then experiment further from that as starting point.  If in a bad room, it may help to angle them so that they are directly PAS, even if that means they are angled less than +/-45 degrees, and you might consider switching the subcards to a more directional pattern like cardioids or supercards.  Outdoors you might want to angle the subcardioids wider, up to +/-90 degrees, as their response should remain well-behaved far off-axis.  That may seem extreme, yet it represents a ~12" spacing / 90 degree inclusive angle between the center microphone and each microphone to either side, akin to two standard 2-ch stereo DIN configs placed adjacent to each other. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: prepschoolalumniblues on February 24, 2020, 01:40:41 PM
Thanks! I'll report back once I have a chance to try it out...

I'd give it a go initially with the supercardioid in the center facing directly forward and the spaced-subcardioid pair angled ~ +/-45 degrees.. then experiment further from that as starting point.  If in a bad room, it may help to angle them so that they are directly PAS, even if that means they are angled less than +/-45 degrees, and you might consider switching the subcards to a more directional pattern like cardioids or supercards.  Outdoors you might want to angle the subcardioids wider, up to +/-90 degrees, as their response should remain well-behaved far off-axis.  That may seem extreme, yet it represents a ~12" spacing / 90 degree inclusive angle between the center microphone and each microphone to either side, akin to two standard 2-ch stereo DIN configs placed adjacent to each other.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: goodcooker on February 25, 2020, 08:22:17 AM

Here’s what I’m currently thinking: I’d like to try wide-spaced subcardioids (using the full width of the bar, 2 feet) with a hyper in the center.

I did this fairly often in the past with Peluso subcard mics as a split pair or in a NOS type arrangement (usually a little wider and not angled as much as 90 degrees much as Gutbucket suggests) with a single hyper mic in the center pointed straight down the middle. Only when I was pretty close to the source less than 50 feet.

It helped give some clarity to recordings made in a specific room that suffered from the line arrays being hung in such a way that in order to cover the very wide room it created a lot of early reflections and made the sound from the audience a little muddy.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on February 25, 2020, 12:08:53 PM
Over in the Izotope RX thread I posted a bit of speculation about the potential of using "de-bleed" type DSP processing on multichannel array sources as a way of manipulating the directivity of channels in the array:

https://taperssection.com/index.php?topic=186865.msg2323770#msg2323770
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: prepschoolalumniblues on February 26, 2020, 06:28:46 AM
Everything you described is pretty much my exact scenario, so I’m glad to hear that you’ve had some success with it. Thanks for sharing and I’m excited to try it out.


Here’s what I’m currently thinking: I’d like to try wide-spaced subcardioids (using the full width of the bar, 2 feet) with a hyper in the center.

I did this fairly often in the past with Peluso subcard mics as a split pair or in a NOS type arrangement (usually a little wider and not angled as much as 90 degrees much as Gutbucket suggests) with a single hyper mic in the center pointed straight down the middle. Only when I was pretty close to the source less than 50 feet.

It helped give some clarity to recordings made in a specific room that suffered from the line arrays being hung in such a way that in order to cover the very wide room it created a lot of early reflections and made the sound from the audience a little muddy.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on March 09, 2020, 06:27:05 PM
Continuing with the OMT8 re-rigging:
Ran the new CDint microdot cable through the snake to the center DPA4098 (M/S Mid) which allowed moving it's XLR adapter from up top down to the recorder.
Covered the raw aluminum center mic-pair adapter with black heat-shrink.
Made small pass-thru for cable snake from main compartment of bag to front pocket, where F8 and Tallentcell battery are housed.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on March 09, 2020, 06:37:30 PM
Cleaned up the center-hub arm supports by removing the ratty gaff tape from the stiff "mustache" wires which support the telescopic antennas, replacing it with heat shrink.  Much cleaner and somewhat better cushioning/abrasion-protection for the telescopic arms and wiring.  Because the stiff support wires were already bent to shape it was difficult threading the heat-shrink around the bends, so I covered each with two sections.  Would be much easier to heat-shrink the straight wire prior to bending, which is how I originally applied the gaff tape.  I've used the original support wire for the past 10 years or so, which was formed from a stainless steel welding rod.  The smaller 'V' shaped one supports the rear-facing pair and is fashioned from plain-steel coat-hanger wire.  Those arms are much more lightly loaded, yet can still droop if the hinge screw becomes loose.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on March 09, 2020, 06:50:48 PM
Getting there..
I next intend to use sections of heat-shrink in place of the remaining gaff tape, most of which secures the wiring and mics to the antenna arms, some of which is used to make the shiny stainless-steel hardware bits matte-black.  That will look much cleaner and more professional up close, will be friendlier to the wire jackets, and eliminate the nasty adhesive goo when re-working things.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on March 09, 2020, 07:22:00 PM
Man, I love seeing this rig.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: b9audio on March 10, 2020, 02:43:38 AM
This is really a good job. Wonder how it sound?
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on March 10, 2020, 08:28:06 AM
It is beautiful! Thank you Gutbucket for the photos.

I have one question. I am using very similar telescopic antennas. I have them attached to the main stand using U-profile with rubber. So the antennas are not conductively connected to the stand. Last time I had some problem with wifi or phone interference. I wondered if I did not make it worse by not having antennas conductively connected to the stand. I know nothing about these problems. I see from the photos that you are using heat shrink on some individual parts. Did you have any problems with RFI?
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: rocksuitcase on March 10, 2020, 09:43:32 AM
Wow, post up that Marco show bro! :P   Thanks for the pictures! Looking great.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on March 10, 2020, 12:20:33 PM
EmmR- Thanks!  It is most certainly oddball. I've very much enjoyed working through its evolution over the years and documenting that here.  Not quite of the same complexity as some of your impressive contrivances though!


b9audio- This array was developed first and foremost for multichannel (7-9 ch) surround playback, yet I've found that most of the fundamental array design choices are directly applicable to producing quality 2-channel stereo output with an especially useful degree of flexibility given the odd constraints under which most members of this forum are recording (non-professional live-performance audience perspective recording).  For years I've been intending to make various samples and full recordings available here.. the absence of which is admittedly appalling. As tapers we are something of an odd bunch, and I suppose this is my particular peculiarity. Along with the high degree of flexibility these arrays provide comes a necessity for proper mixing, and I feel a strong responsibility for doing that properly to really do the recordings justice.  I hope to move forward and get back to proper mixing again, yet life pulls in multiple directions and I don't currently have my editing system or monitoring setup operable. I really need to work toward getting that in place again and am currently listening through headphones to the 2-ch monitor mix direct out of the recorder(s).  I've much respect for other tapers who do get their recordings out!

The primary aspect of this array specific to 2-ch stereo was the addition of the coincident figure-8 to the single center microphone position to form a Mid/Side pair.  This mostly addresses differences in imaging between 2-ch (L/R) and 3-ch (L/C/R) front playback arrangements.  With 3-channel playback the near-spaced L/C/R supercards are routed directly to the three front speakers and the figure-8 goes unused (at this point).  That I introduce an additional (8th) channel for 2-ch stereo only is ironic, but the M/S center pair provides a very useful degree of central image manipulation and helps convey a sense of 3-dimensionality otherwise lost when reducing everything from 7 playback channels distributed all the way around a listener down to 2-channels.  I've stated before that in some ways making a really good stereo recording is more challenging than making a good surround recording since it represents a further abstraction from reality, requiring additional care in crafting the illusion, whereas with the additional playback channels those aspects naturally become less-masked.  Likewise, although making an excellent mono recording requires less gear and setup complications, it represents an even greater challenge in crafting a really good sounding, convincing illusion.


kuba e-  I'm no RFI expert by any means, but I don't think electrically interconnecting the antennas and stand will make an impact on radio interference.  Some unbalanced microphones and cables are more susceptible to RFI than others.  Long ago I had some SoundPro's omnis that were extremely RFI sensitive in comparison to the miniature AT's and DPA I was also using. I'm not actually sure if there is good electrical connection between my antennas and stand or not.  There is no direct electrical connection between the signal chain and the bits of supporting kit.  Best for RFI rejection would be a balanced signal run from the microphones to recorder, but as you can see the only balanced run I currently have is for the figure-8.  I just eliminated the other by moving the XLR adapter for the center directional mic from the microphone down to the recorder itself.  I did so to streamline things aloft, recognizing that I would be increasing susceptibility to RFI somewhat by doing so. But I've not had RFI problems with the other channels, making it an acceptable trade.  There is no way I could arrange to have all seven XLR adapters up at the microphones so as to provide balanced runs up the stand without things becoming too heavy and bulky aloft.   

Certain unbalanced extension cables and connectors will be more susceptible to interference so you might try changing those out and keeping them as short as possible.  EFI rejection in unbalanced runs represents a particular flavor of sorcery, wish I could be of more help on this.


rocksuitcase- you are a big inspiration for me to work toward getting these recordings out!  Marco Benevento last Saturday was a great show.  Super windy out there that night though, and because of that this recording needs even more work than most.  The wind protection provided by the BAS windscreens was simply insufficient.  I was listening last night using headphones directly out of the recorder, going back and forth muting the figure-8 and various combinations of the supercards as required.  As expected, the fig-8 was most affected, but I also noted more wind noise in the in the center and rear facing supercards than the L/R supercards, presumably from wind leaking in through small gaps in the rear-cuff of those due to my mounting arrangements for those channels. Will consider ways to improve that. As expected, the sphere-mounted omnis with the thinner foam screens fared far better, with wind rumble only apparent in a few spots. 

Spyder 9 (Dan) also recorded using Nak1000 cardioids, but I've not checked with him since to see how much the wind affected his recording. I started with my array up quite high, which works best there when wind is not an issue.  I kept lowering the stand partly due to potential blow-over theat and partly in a futile search for less intense blowing down low, ending up at around about 7', same as Dan's rig.

Keep your ears open for the opening act, a local Miami instrumental band named Electric Kif, one of my favorite regional acts for several years that is astoundingly good and is starting to gather wider acclaim.  I think you'd really dig 'em.

Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on March 11, 2020, 10:17:29 AM
Thank you Gutbucket for writing about your experience with RFI. Probably the place, where I was recording, had very strong wifi signal. I taped with chopped Nak300 in xy and spaced Dpa4061 on the antennas. The reason why I asked about antennas was that Nak300 had no interference. So my first suspicion was the antennas. Yes, all signals were unbalanced (Nak300->ca9200->dr2d + Dpa4061->second ca9200->dr2d). And I also soldered all connectors by me at home, maybe I didn't properly connect the cable shielding. I should check all my gear.

I understand you about releasing recordings. And I also respect people here that are releasing their recordings. I am taping very little and mostly only my friends. They are happy to listen to the recordings but it takes me too long to finish it. Even then I am not satisfied with my mix. Unfortunately, I don't have the discipline to return to the recording after some time. I'm sure OMT provides a lot of options. Because playing with OMT I am more aware now of some aspects of recording - center and sides of stereo image, direct/reverb ratio and specially the third dimension or some kind of fullness. I love when some recordings have the third dimension. Some audience or matrix recordings sounds great on stereo playback. When audience recording has this magic I am able to overhear even some major troubles.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on March 13, 2020, 04:45:22 PM
I'm sending a few photos of how I connected the antennas to the microphone bar. It's from the remnants I found in the workshop. I have the antenna wrapped in rubber and push it into the U profile. It holds tight. Assembly and disassembly goes fast.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on March 13, 2020, 05:03:25 PM
Slick!  Digging the press-in friction mounting of the antennas via deformation of the rubber "bushings".  It's innovative, simple, low-profile, and appears to be quick to setup and break down. Nice work!
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on March 13, 2020, 06:50:08 PM
dig it
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on March 13, 2020, 08:54:17 PM
Thank you. It is nice from you.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: rocksuitcase on March 18, 2020, 02:07:26 PM
Slick!  Digging the press-in friction mounting of the antennas via deformation of the rubber "bushings".  It's innovative, simple, low-profile, and appears to be quick to setup and break down. Nice work!
Yeah kuba, very slick! I really like this approach to the wide small omnis. +T
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on April 12, 2020, 03:09:38 PM
Question for the OMT experts.  I'm finally getting around to working on my JRAD Red Rocks recording from last summer.  I ran DPA 4061s spread as wide as I could...at least 15 feet I'd say.  Going into the show I was planning on sticking with just that but for the hell of it I took a patch from Todd R's MG M200 rig that was set up in the center of the "section" (and thus about the center of my DPAs).  I figured I could use those sweet sweet MGs to fill in the center of the DPAs if needed.

When I started mixing them together, though, the stereo image got weird at times.  It's most noticeable on a guitar solo, where it will sound like it starts to come from one side then shifts to the other side (left/right in the stereo image, that is).  I kept track of which mics were in which channel so I'm pretty confident I don't have the L/R channels mixed up.  I did try swapping the channels of one set of mics and that seriously messed things up so I don't think that's the issue.  Todd's mics were in a near-spaced configuration...I think it was approximately DIN.

Does anyone have an idea about what could be going on here?

I chickened out and only posted the DPAs.  If anyone is bored and wants to take a crack at mixing the sources just let me know and I'll get you the master files.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on April 13, 2020, 11:13:56 AM
^ Sounds good here straight up Lucas.  Enjoying it this morning, thx.  Currently rollin' the sweet Bird Song.


I had some fun messing around with OMT in a giant sewer pipe the last couple weekends- https://taperssection.com/index.php?topic=194159.msg2327608#msg2327608
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on April 13, 2020, 04:44:10 PM
^ Sounds good here straight up Lucas.  Enjoying it this morning, thx.  Currently rollin' the sweet Bird Song.


I had some fun messing around with OMT in a giant sewer pipe the last couple weekends- https://taperssection.com/index.php?topic=194159.msg2327608#msg2327608

Thanks.  If nothing else it's interesting to switch back and forth between my recording and the official recording, because it really illustrates that "hole in the middle" effect from listening to just the wide-spaced omnis on their own.  Which is not to say that I think mine is bad, it's just a radically different presentation of the sound.

I'd love to hear some of the sewer pipe stuff!
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on April 13, 2020, 05:57:06 PM
Was good fun playing into opposite ends of the shorter pipe length a couple days ago, mostly doing simple 2 chord jams for her to practice simple yet timely fingering changes.  I'll have to listen to see if we were able to make it through a complete segment without embarrassment!  Only brought the phone along for that session so as not to intimidate the fresh upstart talent on the other end.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on July 31, 2020, 11:21:10 AM
Linking this post I made over in The World's Finest Blumlein Array (https://taperssection.com/index.php?topic=194934.msg2336669#msg2336669) thread.  In it I posted about a realization of why I think the approaches covered here are important at a basic fundamental "gestalt" level if you will.  Although that realization isn't particularly new, it has grown increasingly clear to me as I progress along my own taping journey.

Len's links to derivations of virtual arrays of two and three 2nd order hypercardioids in comparison to Blumlein (https://taperssection.com/index.php?topic=194934.msg2336263#msg2336263) are what sparked my reflections and serve as notable data-points applicable to OMT.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on October 11, 2020, 04:51:55 PM
Almost two years late, I finally got around to this one: https://taperssection.com/index.php?topic=195497.0

I ran AT4031s 13" and 110* apart.  In the center I ran AT853 subcards facing directly forwards and directly backwards.  I didn't end up using the rear-facing mic.  There was already more than enough room sound for my taste, and I didn't think the recording benefited from having it in the mix.  Speaking of the mix, I ended up using more of the center mic than I initially imagined I would.  There was a point where it really seemed to anchor everything, and I went with that.  I did some fairly mild EQ once the three mics were mixed down to stereo.  Unfortunately, I don't think the sound was all that great that night.  The bass is largely lost in the mix, and the low end is mostly mush other than the booming kick drum.

For anyone interested in a comparison, here's Ricky's recording from the same stand, but he was using a PAS configuration: https://archive.org/details/Spafford2018-10-27.AKG.P170.AUD.flac16 and here is another source...I think this stand was about 10 feet closer than us, but way towards the stage right side: https://archive.org/details/Spafford2018-10-27.Spafford.Ogden.Denver.DarKeLive
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: fireonshakedwnstreet on October 11, 2020, 07:08:25 PM
Almost two years late, I finally got around to this one: https://taperssection.com/index.php?topic=195497.0

Nice warm sound and has some punch.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on October 11, 2020, 09:15:21 PM
Almost two years late, I finally got around to this one: https://taperssection.com/index.php?topic=195497.0

 Unfortunately, I don't think the sound was all that great that night.  The bass is largely lost in the mix, and the low end is mostly mush other than the booming kick drum.

For anyone interested in a comparison, here's Ricky's recording from the same stand, but he was using a PAS configuration: https://archive.org/details/Spafford2018-10-27.AKG.P170.AUD.flac16 and here is another source...I think this stand was about 10 feet closer than us, but way towards the stage right side: https://archive.org/details/Spafford2018-10-27.Spafford.Ogden.Denver.DarKeLive

Sounds good.  The comparisons are interesting.  See what you mean about the kick.  Common problem in one club here.  You might try some tricks in RX7/8 Rebalance, might be able to make some bass to even up against that kick.  I'm in the process of pulling apart a mono 4060 recording and equalizing the stems separately, pretty amazing what the RX8 update will do. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on October 12, 2020, 09:57:47 AM
Thanks Heathen, the recording sounds pleasant. From my little experience, when I recorded couple times with the rear microphone far in the audience, it turned out that it is better to first use a pair xy in the center and only when the channel is free, then add a rear microphone. When I have xy, I can make an m/s adjustment and that is a big advantage for me over the single forward microphone. But maybe your configuration can be successful when we are closer to the stage.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 12, 2020, 06:55:14 PM
Thanks for posting the recordings Heathen.  Its informative to be able to compare with the two other recordings.  Listening around the general frequency response differences, which is almost always the first thing I notice and recognizing that influences perception of other aspects, I hear more 3 dimensionality in your recording which is one of the things I've come to expect from an OMT arrangement.  Interestingly, I notice more audience pickup in the Ricky's PAS stereo pair.  That's somewhat surprising as I imagine the PAS angle from the recording position you both shared was likely significantly less than the 110° used between your AT's.


This brings to mind something I find useful in considering how an arrangement of microphones works in a collective sense.  Not with regards to stereo image pattern overlap, but in terms of overall sensitivity and how that sensitivity is distributed. I've posted previously about the overall sensitivity pattern of an array. By which I mean the collective combination of all microphones in the array in sort of a monophonic sense, at least in that they overlap each other and produce a collective sensitivity pattern "shape".  We modify this collective sensitivity pattern before recording by choosing the patterns, angles and positions of the microphones which form the array.  We further modify the shape of that pattern afterward by choosing which channels to include and adjusting their levels relative to each other.  One thing adjusting the level of the center microphone channel against the Left and Right microphone channels does is modify the shape of the collective sensitivity pattern of the array.

The entire picture is considerably more complex, but this way of thinking is a useful simplification for illuminating the most fundamental aspect of an array's overall sensitivity to the 3d sound field in which it is immersed at the recording location.

On the Sengpiel Audio stereo microphone array visualizer [http://www.sengpielaudio.com/HejiaE.htm (http://www.sengpielaudio.com/HejiaE.htm)], the collective sensitivity is represented by a single grey pattern line which surrounds the two smaller, individual microphone pattern lines in red.  When initially loaded, the virtualzer defaults to an EBS microphone setup, which is a pair of cardioids spaced 25cm and angled 90° apart from each other.  The polars of the individual microphones in red are cardioid shaped. The collective sensitivity pattern of the two in combination is shown in grey and also cardioid shaped.  It's actually something of a directly forward-facing subcardioid.  If you change the angle between mics from 90° to 0° the collective pattern tightens up to a true cardioid.. if you change the angle to 180° it widens into more of a circular shape, indicating a more omnidirectional collective sensitivity for the combined array of two cardioids facing away from each other.

I'm thinking of recording in a room as a "sensing problem", first simplified to this kind of overall collective sensitivity shape (sort of the monophonic case if you will), then further differentiated with a careful ear towards the interactions between whatever divisions we choose to further impose on it.

Like a single omni, a Blumlien 90° crossed pair of fig-8's, or an ambisonic microphone (each of which have equal sensitivity across all horizontal directions) most multichannel OMT arrangements also have sensitivity across the entire horizontal plane.  That's because they commonly include omnis and/or include directional microphones that are generally pointed so as to cover all cardinal directions, at least to the degree that their patterns overlap and provide sensitivity to direct sound arrival across all horizontal directions.  We gain some control over the shape of that collective horizontal sensitivity by way of the physical arrangement of the microphones. We further modify that collective sensitivity pattern by choosing which channels get used, their routing (which get assigned to the Left output channel, which to the Right, which to both), level adjustment, EQ or other filtering, Mid/Side ratio adjustments, and perhaps subtle panning adjustments as necessary.  The key is that we gain deferential control over sound arriving from different portions of the horizontal plane to some degree, both prior to and after making the recording.

The stereo and 3d cues are generated by differences between the microphone channels. In addition to those cues picked up from the environment itself, they include differences in phase, time-of-arrival, and response due to the particular microphones used and how they are positioned and oriented with respect to each other.  In other words, they are both "of the environment" and "of the array" in terms of the way in which the array is energized by the sounds in environment (and how we further modify the interaction of channels in the mix). Such "of the array" interactions are inevitable, so we should make sure the interactions between the microphones themselves make for positive, or at least neutral additional cues which don't end up doing more harm than good.  That gets tricky.

Binaural human hearing is similar in that it is collectively omnidirectional in the overall sense, yet differentiated in such a way that we are able to determine direction and other auditory attributes.  Similarly, the raw data contains cues that are both "of the environment" and "of the interactions of our sensing array".  The cues are complex, not simply level and time-of-arrival based.  Our brains, formed by evolution and trained by life experience filter and interpret the data in such a way as to consciously ignore the base-level interactions particular to the sensing array of funny shaped ears placed on opposite sides of an actively articulated head - the end result being conscious perception of directional cues and other high level auditory aspects, without noting level, spectral, and timing differences directly.  It either works right, or it doesn't. If it doesn't something may seem "off" and to some extent we can train ourselves to be more consciously aware of such things, or it might just sound bad or lacking or flat or involving or whatever.

We do well to design our artificial hearing array mic setups in such a way as to play nicely with the expectations of our brains.  And by play nicely I mean trick ourselves into believing the auditory illusion is convincing.  Beyond the ability to stack the deck by devising clever microphone arrangements and manipulating the resulting channels in the ways we do currently, there are a clear paths forward toward creating more sophisticated auditory illusions using the recordings we are making today.  I can already do that to some extent by manipulating for playback over more than two speakers, using relatively simple forms of multichannel surround playback.  But I also know of and foresee various ways of making more convincing illusions over 2 speakers or headphones by more complex manipulations of the differentiated data we collect, making for a better fit to the complexities of the human hearing sensory array and producing an even more convincing high-level conscious experience. 

I might be reaching a bit, but I think the careful adjustment of the center mic channel level verses the other two in heathen's recording represents an important step in that direction.  Consider how adding a second microphone channel to mono is able to change our perception so dramatically by producing a far more robust stereo illusion of the original event.  The big change is not the addition of another channel" but what our brain does with the additional information it is able to provide.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: fireonshakedwnstreet on October 12, 2020, 11:35:36 PM
I absolutely love the philosophy behind OMT. Though I may not understand all the technical aspects, I know these recordings just have a little something more than your "traditional" recording. Thanks to gutbucket and all the other contributors for the knowledge on this thread. I am just getting into taping and have been using OMT. I will also add that for the beginning taper that does not have a great all around pair of mics, OMT is a great way to get a good overall product with less than stellar mics. Gonna pick up some hypers and 8s for some more experimentation next year.

Here is a recording (Nak cp2/SamsonC02/AT 853Rx cards) of a local GD cover band I made last week. Regarding the mix I cut some of the mids and highs as the guitars were just piercing. I also smushed down some really loud vocals throughout the show. I am also posting a link with mp3s of the CP2s and Samsons alone, as well as combined for comparison with the final six channel mix.

https://archive.org/details/touchofgrey2020-10-03_202010/tog2020-10-03.flac24 (https://archive.org/details/touchofgrey2020-10-03_202010/tog2020-10-03.flac24)
https://drive.google.com/drive/folders/1b247Tir6sa0H2X0oF-bTtOEWeVsA414A?usp=sharing (https://drive.google.com/drive/folders/1b247Tir6sa0H2X0oF-bTtOEWeVsA414A?usp=sharing)



Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 14, 2020, 11:16:43 AM
Hey fireon,

Good to hear you are enjoying making recordings this way, and thanks for posting the links.  I'll make some observations and suggestions in a following post. 

First I want to talk a bit about how and why I agree with your statement about these techniques being able to get the most out of less expensive microphones.  An important part of my own path to this point has been determining what level of performance is required to achieve results that meet or exceed my own quality standards when used in these unusual arrangements, within the constraints of cost, robustness, size, weight, and other considerations.

When I really got into playing around with additional channels and how best to incorporate them into what later became dubbed OMT, I was using odd combinations of top quality and less expensive microphones. The top quality mics are my personal reference for how I expect high quality directional microphones to perform.  Acquiring and using them helped better tune my ear and mindset to what "top quality" really means in terms of extended frequency response, smoothness of response, off-axis pattern behavior, low noise and more subjective subtle qualities of depth and imaging, in a hands-on way I which could not achieve by simply listening recordings made by others.  My familiarity with the nuances of their use and performance in regular 2 channel stereo configurations translated as a reliable level of confidence in making decisions about the unusual multichannel OMT setups.  That helped reassure me that my assessment of any shortcomings of the oddball setups I was experimenting with would not be limited by the performance of the microphones themselves, but rather by how I was employing them or other external factors.  In that way they served as a quality-performance reference against which I could determine how well smaller, lighter, less costly and precious mics might be able to be substituted in their place.

At the same time, I was also using low cost mics, sometimes borrowed, to create setups I could not easily or safely achieve using my larger, heavier, more delicate reference mics. They served as a way to test some setups that I could not otherwise achieve or easily deploy in many real world taping situations.  That way of approaching the problem from opposite directions helped in converging on practically achievable arrangements I could reasonably deploy wihtout worry, capable of achieving a level of quality I was fully satisfied with.

The short and long of it is that I decided somewhat lesser quality mics could work satisfactorily for me, yet I still wanted something higher quality than the miniature directionals I had been borrowing.  I started looking for the best quality miniature low-powered cardioid/supercardioids I could find.  I found what I thought might work and ended up making a few 2-ch stereo test recordings using all three categories of mics in the same configuration at the same time - 3 separate stereo pairs for comparison.  I could easily hear a difference between each of the three, and after playing around with the resulting recordings a bit, I made the following initial conclusions:
1) I decided that for straight 2-channel stereo recording, I felt I needed the top quality mics to achieve a really excellent quality I would be completely satisfied with.
2) Using my best microphones as the quality reference, I found I could get similar results from the very good quality supercardioid candidate with some EQ adjustment, after which they only really came up short in the more subtle subjective nuanced qualities relating to imaging and 3d depth qualities.
3) I found I could somewhat improve the low cost pair to some degree, yet not to the same extent, and not with the same degree of ease as the better quality candidate mics.

At the same time, I'd determined that the early OMT arrangements hinted at achieving similar nuanced qualities of imaging and depth using lesser quality microphones.

I decided there was no way I could afford 6 to 8 channels of top-most quality mics needed to achieve the OMT setups I wanted to use, and doing so wasn't really practical for my intended uses anyway.  Instead I decided to follow the path of a sufficient number of good quality mics that I new I could use and manipulate the way I wished to employ in unique ways, instead of a pair or two of really top studio-quality mics configured in the way I would need them (using active cables and all that).

So in one way I determined that my best mics really are best!  But I also determined that I could get very close to the same quality level using somewhat less expensive microphones that were a far better fit for my uses in most other ways, and actually exceed those results due to the way that allowed me to use them.

I guess what I'm trying to convey is this- 
> Using these somewhat complicated multichannel setups can be fun! 
> I think it's useful to work from a strong foundational understanding of basic 2-channel stereo recording, both in theory and practice.
> One can then sort of simultaneously throw away much of the specifics of traditional 2-channel techniques (which I feel is necessary for really extending things in the most useful ways) while still using the basic relationships and insights to inform the extension to additional channels. This represents the most difficult step for most tapers.
> Make the most of what you've got, and think carefully about where you want to go with it.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 14, 2020, 11:22:32 AM
Apologies to anyone following along for the excessive length of my last couple posts. I realize I'm really missing recording and our discussions here about it, and that gets me waxing on a bit much.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on October 14, 2020, 12:30:51 PM
I absolutely love the philosophy behind OMT. Though I may not understand all the technical aspects, I know these recordings just have a little something more than your "traditional" recording. Thanks to gutbucket and all the other contributors for the knowledge on this thread. I am just getting into taping and have been using OMT. I will also add that for the beginning taper that does not have a great all around pair of mics, OMT is a great way to get a good overall product with less than stellar mics. Gonna pick up some hypers and 8s for some more experimentation next year.

Here is a recording (Nak cp2/SamsonC02/AT 853Rx cards) of a local GD cover band I made last week. Regarding the mix I cut some of the mids and highs as the guitars were just piercing. I also smushed down some really loud vocals throughout the show. I am also posting a link with mp3s of the CP2s and Samsons alone, as well as combined for comparison with the final six channel mix.

https://archive.org/details/touchofgrey2020-10-03_202010/tog2020-10-03.flac24 (https://archive.org/details/touchofgrey2020-10-03_202010/tog2020-10-03.flac24)
https://drive.google.com/drive/folders/1b247Tir6sa0H2X0oF-bTtOEWeVsA414A?usp=sharing (https://drive.google.com/drive/folders/1b247Tir6sa0H2X0oF-bTtOEWeVsA414A?usp=sharing)

Listening to this briefly, as well as the individual samples (thanks for posting those!), I wonder if this would be a good occasion for using a pretty aggressive low pass filter (or a broad "scoop" that leave only the lows and very "airy" highs) on the omnis.  I know that's been done, and talked about, before in OMT land.  If I wasn't on my work computer I'd give it a try with the samples you posted, but I also wonder if it's something you tried in mixing this down?
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 14, 2020, 01:09:43 PM
^posted while I was typing the post below and I agree.


Here is a recording (Nak cp2/SamsonC02/AT 853Rx cards) of a local GD cover band I made last week. Regarding the mix I cut some of the mids and highs as the guitars were just piercing. I also smushed down some really loud vocals throughout the show. I am also posting a link with mp3s of the CP2s and Samsons alone, as well as combined for comparison with the final six channel mix.

https://archive.org/details/touchofgrey2020-10-03_202010/tog2020-10-03.flac24 (https://archive.org/details/touchofgrey2020-10-03_202010/tog2020-10-03.flac24)
https://drive.google.com/drive/folders/1b247Tir6sa0H2X0oF-bTtOEWeVsA414A?usp=sharing (https://drive.google.com/drive/folders/1b247Tir6sa0H2X0oF-bTtOEWeVsA414A?usp=sharing)

Quote from: details from LMA
Source: Six Channel OMT AUD Mix
              Channels 1&2: Nakamichi CM300 (cp2, omnis), spread 32”> Tascam DR70D (24/48)
              Channels 3&4: Samson C02 (supercards), X-Y PAS> Tascam DR70D (24/48)
              Channels 5&6: AT 853Rx (cards), 0 (front) and 180 (rear) degs> Tascam DR40 (24/48)

- Channels 1&2 amplified to -3.0db
- Channels 3&4 amplified to -6.0db
- Channels 5&6 summed to mono amplified to -8.0db
- Eq: Treble -3.0db; 2db cut @ 1khz - 8khz

A few thoughts-
First I'd love to hear more of the omnis, their low frequency content in particular.  Also more of their diffuse decorrelated hf content, but mostly more bottom heft.

With the PAS X/Y pair in the center, I'd re-purpose the single front-facing cardioid. They are overly similar in what they are doing, all the more so given what I presume is a relatively narrow X/Y angle to achieve PAS.   X/Y generally doesn't need any additional center reinforcement even with a relatively wide angle.  The single cardioid would be more useful elsewhere. 

One thing I'd consider is using two rear facing channels instead of one, spaced apart, maybe half as much as the omnis.  That will do two things: help pull rear-arriving content out of the hard center position clearing that space for front X/Y imaging; and help diffuse and distribute that content across the playback image for a greater sense of width and openness.  You can angle them a bit if you like, but mostly keep them facing directly away from the sound arriving from the front. Parallel is OK. 

The other thing I'd consider is pointing that spaced rear-facing pair forward.  Depends somewhat on if there is good ambience in back or not, and how clear the direct sound from the stage sounds at the recording location.  If its very clear sounding there the X/Y pair and omnis should need no help on that account and I'd go with the rear facing pair.  However, if there is no good ambience from back there anyway (only a few feet to the wall in back or whatever) and you need help with "reach" from a distant recording position, then using them facing forward will help.  As with them rear-facing, place them about half way out between the center X/Y pair and the omnis. Angle them +/- 45°, in situations in which you can't get the omnis wide enough apart to achieve good openess and envelopment from them you can angle them apart more.  I would not angle them less than +/- 45° because you already have the forward facing pair in the center (same for a singe center channel).

Now consider that those two arrangements are actually very similar except for how the microphones are angled.  In both cases they are "halfway out" between the center and the omnis.  This makes for a good standard-setup OMT arrangement in terms of mic positions.  You can decide how to point the mid-spaced pair once you assess the recording situation at the venue, angling them anywhere between (+/-) 45° to 180°.  45° maximally increases forward sensitivity and rearward rejection.  It even achieves some degree of increased "phased array" forward reach by presenting five sampling points arranged along a horizontal line, at least is seems to do something like that as assessed by listening, but I won't armchair speculate too much about that.  Pointing them 90 degrees to the sides increases the sense of stereo width and openness and decreases its interaction with the center pair.  This makes the array similar to an OCT (Optimum Cardioid Triangle) setup sometimes used professionally for feeding the front L/C/R channels of a 5 or 7 channel surround recording.  Pointing them 180° maximally rejects the direct sound from the front, allowing you can dial in more ambient richness from the rear before it conflicts with the other stuff.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 14, 2020, 01:17:50 PM
Oh yeah, got side-tracked on the mid-spaced pair stuff..

I also hear some leftward stereo balance predominance in the image, and a less than solid center.  Try balancing the omnis alone first, as well as the X/Y pair alone first, seperately from each other.  Keep the omnis hard-panned, but you can adjust the X/Y pair stereo balance by both level and by panning each side (which is essentially the same as making an individual M/S width adjustment on each side). Sometimes its not possible to center the image without ending up with too much energy on one side, and other times even though each pair might sound relatively balanced on their own, their mix combination skews things to one side or the other. Since you have that mono center mic you can also pan that toward the opposite side to compensate, which tends to work really well for both gross adjustment and fine-tuning of image center placement.  You might also play with polarity in case something got inverted somewhere, which can pull things toward one side.  Like everything, sometimes best is making smaller level/balance adjustments to each part.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: fireonshakedwnstreet on October 14, 2020, 01:32:09 PM

Listening to this briefly, as well as the individual samples (thanks for posting those!), I wonder if this would be a good occasion for using a pretty aggressive low pass filter (or a broad "scoop" that leave only the lows and very "airy" highs) on the omnis.  I know that's been done, and talked about, before in OMT land.  If I wasn't on my work computer I'd give it a try with the samples you posted, but I also wonder if it's something you tried in mixing this down?

Thanks for the feedback! That's interesting. No I haven't tried that with my rudimentary EQ skills. Would you say cut from 300 - 5000?
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: fireonshakedwnstreet on October 14, 2020, 01:40:13 PM
Thanks for the great suggestions, gutbucket! Will continue to play with the EQ and mixing, matching things up.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on October 14, 2020, 04:00:30 PM

Listening to this briefly, as well as the individual samples (thanks for posting those!), I wonder if this would be a good occasion for using a pretty aggressive low pass filter (or a broad "scoop" that leave only the lows and very "airy" highs) on the omnis.  I know that's been done, and talked about, before in OMT land.  If I wasn't on my work computer I'd give it a try with the samples you posted, but I also wonder if it's something you tried in mixing this down?

Thanks for the feedback! That's interesting. No I haven't tried that with my rudimentary EQ skills. Would you say cut from 300 - 5000?

Ideally you'd adjust the EQ setting while listening to it in order to find what sounds best, but as a rough starting point I think you're in the ballpark.  If I was to throw numbers out there, I'd probably start with the LPF somewhere in the neighborhood of 250 Hz, and the HPF somewhere around 7-8,000 Hz.  If you found the guitars too piercing originally, boosting at 5k might exacerbate that so I'd probably start higher.  You might even go up to 9-10k.  It's the "air" you're going after in this approach.  Once you get the EQ set to where you feel like you're capturing the rich lows and airy highs of the omnis, you'll have to mix it in with your directional mics and listen to how they mesh.  Be prepared to go back to the drawing board with the EQ of the omnis at that point :)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 14, 2020, 04:15:29 PM
^posted while I was typing the message below and I agree.   ;)  Note that we both suggest pretty much the same thing  ..and I just assume people are listening while making any EQ or mixing choices.


Might first try simple high and low shelf filters, which work like traditional bass and treble controls.

I'm on a computer where I can't currently listen, but I'd try boosting somewhere below 200Hz and 10kHz and above to start.  If you do that separately you can control how much in each region to taste.  Cutting between there is the same in essence, and both may be used in combination, but does not give you separate control over how much bottom vs how much top on its own. 

Scooping out the middle range makes more room for the X/Y pair to do its thing and may reduce some of the mid/upper-mid stridency.  It also emphasizes the ranges in which the omnis tend to best contribute.

Quote
- Channels 5&6 summed to mono amplified to -8.0db

I'd not sum these.  Not prior to mixing for sure, and I can't think of any particularly reason to do so afterward other than in the mix itself.  Best to have the rear-facing channel(s) on a separate fader which can be muted easily and brought up last.  Get everything else working as best it can, then sweeten with some of that.  I generally keep the rear content level just below the point where it becomes noticeable, such that it is only really obvious in its absence.

Here's how I'd approach this mix:

The preparatory stage-
1) Start with the omnis alone.  Hard pan them Left/Right.  Balance the image by adjusting the level of each.  EQ as necessary for them to sound good and well balanced. Add bass if lacking, add middle if it needs it even if you end up scooping the mids later.  You can EQ each side somewhat differently if that helps balance things, just make sure it sounds natural with just the omnis alone.
2) Mute the omnis.  Bring up the PAS X/Y pair alone.  Hard pan them Left/Right.  Balance the image between them by adjusting the level of each. EQ as necessary for them to sound good and well balanced, but don't worry about any lack of bass.  This EQing may be more about fixing any overly aggressive mid or upper mid-range stuff that sticks out.  If it helps you to get the EQ elsewhere adjusted correctly, bump up the bass some if it needs it, then remove the bass correction after you get the EQ across the rest of the range correct sounding. You can try it with that bass correction left in, but most of the bass should end up coming from the omnis and many times it works best if the directional channels are a bit lean at the bottom.
3) Mute the X/Y.  Bring up the single center forward facing cardioid.  Pan it to center.  EQ as necessary for it to sound good.  Don't worry about lack of bass.  Same deal with addressing any aggressive frequency range that sticks out.
4) Mute the forward facing cardioid.  Bring up the rear-facing cardioid. Pan it to center (1).  EQ as necessary for it to sound good but don't worry about clarity of the music or vocals.  It should sound natural, but like listening from far  away.  Often helps to cut mids and give this a bit of loudness type curve with more bass and highs.  Mute the rear-facing channel.

The mixing stage (where the fun is)-
5) Unmute the omnis.  Unmute the X/Y pair.  Adjust levels of the pairs and play around with the balance between the two.  Don't change the level relationship within each pair you established in the first stage, only between the two pairs.  There may be a couple different balance relationships which work well.  Listen for different things in deciding which works best- overall frequency balance, image width, center solidarity, image depth, etc.  Listen for a while to get your brain familiarized with what you have.  It may be good just like it is.
6) Unmute the single forward-facing cardioid.  Adjust level and listen for what it does.  Is it making things better or worse?  Now is the time to have some comparative fun. Mute the X/Y pair.  Go back and forth between just omnis and mono center cardioid and just omnis and center X/Y pair.  Interesting.  Maybe tweak some EQ on the mono center cardioid and see if you can improve just omnis + mono center cardioid.  OK enough comparative fun, lets get back to the mix.  As a monophonic channel the addition of this to the mix will solidify the center if that is needed, but compare that to keeping it muted and adjusting panning of the X/Y pair, bringing in each side from the previously hard-panned L/R positions (2).  It might be better to keep the X/Y pair hard-panned and use some of the mono center cardioid to bolster the center image, maybe not.  It might help to pan the mono center cardioid to one side to correct the overall balance with the other pairs unmuted.  Maybe you don't end up using any of the mono center cardioid.  Determine what works best.
(7) Unmute the rear-facing channel and bring it up.  Listen for what it does.  Listen for what goes wrong when its level is overly high.  Bring it back down and determine if it makes things better when there is some but not too much of it.  Find the level where it is no longer audible.  Mute and unmute to see if it still makes a difference.  This part will be strongly affected by the what is going on in the recording at the point in which you are listening.  You  are likely to want more of it during sparse low level music and between songs, and less when the music gets loud, or when there are distractions back there. (Aside- keeping as much direct sound arriving from the front out of the rear facing channel(s) as possible by way of your microphone arrangement reduces the need to ride this level as the program changes and makes it easier to decide on an appropriate level for it).

8 ) Save.  Play around and revisit things and see if you can make it better.  If you think you did make it better, come back later and compare with what you saved before you started second guessing.

Extra credit (a couple more advanced things you can try that often work well)-
9) See footnote (1) above.  Adjust EQ on the rear-facing channel to as before as necessary, but instead of leaving it panned to center, duplicate it to an adjacent channel (or make it a stereo channel or whatever).  Hard-pan these two channels Left/Right.  Invert polarity on one of the two.  Try this in place of a center panned monophonic rear facing channel.  If it works you get more ambient width, a less cluttered center for the stuff from the front, and may be able to use more of that channel in the mix than you otherwise could.  If it doesn't work, you can just go back to the monophonic rear channel panned to center.  This technique or variations on it can also be useful when there is only a single monophonic center forward facing channel instead of a coincident pair.
10) See footnote (2) above.  You can actually play with "over-panning" the X/Y pair "superwide" (maybe to make room for the monophonic center cardioid, or maybe just on its own).  Doing so is essentially a Mid/Side ratio readjustment.  So is simply panning both sides equally toward center which decreases width and increases "Mid", but this allows you to go wider than hard-panned.  You can use a Mid/Side tool to do that and increase the level of Side, or your editor may change the standard pan control to a stereo-width control when the channel is a stereo channel rather than a mono channel.  A stereo width control often has mono as one extreme position, normal hard panned L/R in its center position, and "over-width, super stereo" as the opposite extreme position from mono. Regardless of how its done, that kind of Mid/Side stereo-width adjustment to the X/Y pair is very useful for dialing in the perfect image blend between the omnis and the center.  Its a very useful technique for any coincident pair, particularly well suited for optimizing a PAS X/Y center pair which might otherwise be a bit narrow on its own due to a narrow PAS mic angle.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: fireonshakedwnstreet on October 14, 2020, 04:22:52 PM
Thanks gentlemen for your detailed and very informative responses. Definitely have a plan of attack now!
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on October 14, 2020, 05:08:07 PM
One thing I'll add that may seem obvious but I sometimes still have to remind myself about is don't feel obligated to use all the mics in your final mix.  (Edit: looking back at Gutbucket's most recent post I see that he's pretty much said this already...apologies for the redundancy on my part.)  If some don't contribute anything worthwhile, or cause more problems than they solve, feel free to leave them out.  Don't feel bad about not using them...feel good that you had the stones to go out and experiment!

And since it just popped into my head, if anyone following along ever wants to mess with some OMT stuff I'm happy to make the raw original files of anything I've recorded available to whoever has any interest.  (Not that my recordings are anything special, but it's all I've got.)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on October 14, 2020, 05:30:52 PM
One thing I'll add that may seem obvious but I sometimes still have to remind myself about is don't feel obligated to use all the mics in your final mix. 

Yes!  I put up more than I generally use, sometimes it all makes it's way in, many times not. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: rocksuitcase on October 15, 2020, 10:06:35 AM
One thing I'll add that may seem obvious but I sometimes still have to remind myself about is don't feel obligated to use all the mics in your final mix. 

Yes!  I put up more than I generally use, sometimes it all makes it's way in, many times not.
I have to add a YES here. Putting up the 6 or 8 channels, by itself, is an exercise. So using all the channels in the mixdown is my usual goal, but if I need to cut the rear mic or mix the center down to X-Y or one single fwd facing mic, it's all good. Whatever the ears tells you at some point. With the omni channels one has to resist the urge to EQ down too much bass, often it needs reduced, but I found at first I was dropping the low freq's too much for my final mixdown listeners. i.e. drop it 2-3 dB vs 5-6 dB as a tiny example.

I listened to fireonshakedowns show, about five tunes. You can hear the dimensionality of the OMT mix immediately. I felt the show sounded right on. Thanks for sharing.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on October 15, 2020, 06:16:35 PM
The other thing I'd consider is pointing that spaced rear-facing pair forward.  Depends somewhat on if there is good ambience in back or not, and how clear the direct sound from the stage sounds at the recording location.  If its very clear sounding there the X/Y pair and omnis should need no help on that account and I'd go with the rear facing pair.  However, if there is no good ambience from back there anyway (only a few feet to the wall in back or whatever) and you need help with "reach" from a distant recording position, then using them facing forward will help.  As with them rear-facing, place them about half way out between the center X/Y pair and the omnis. Angle them +/- 45°, in situations in which you can't get the omnis wide enough apart to achieve good openess and envelopment from them you can angle them apart more.  I would not angle them less than +/- 45° because you already have the forward facing pair in the center (same for a singe center channel).

I like this approach a lot. When I recorded in a room with good acoustics, both pairs omni and xy were good on their own and it was easy to mix it. Then it have to be great to be able to add a pair of spaced rear facing cards. I haven't recorded with a stereo rear pair yet, but I assume it will be better than mono rear and it will be easier to mix it.
I also recorded in rooms with bad acoustics. In this case, omni didn't sound good on it's own and I used more xy in the final mix. If I had forward spaced cards at 45 °, I assume it would help, because I would partially or fully replace the omni with it.

Fireonshakedwnstreet, It have taken me a long time to get a little confident with mixing. And it's still difficult for me. But over time, I hear more and more details that I was not aware of before. Patience is needed. And the more recordings, the better.

My mixing procedure is according to Gutbucket advices:
Process the stereo pairs on their own.
Choose the main pair that sounds better on its own, either xy or omni.
Make a solo for the main pair and gradually adding a second pair until it sounds great.
The continuous check is to solo/mute omni/xy
Adjust mid/side ratio on xy
Try effects on individual stereo tracks(eq of omni or xy ...)
The continuous check is to on/off the effet
And the last, adding a rear mic to the mix

I didn't make many recordings. I have never been successful with lpf on omni. It always sounded a little weird to me. I'll have to try again sometime.  What I like is mid/side manipulation. I'm trying it not only on xy, but also on spaced pairs sometimes. I also like mid/side eq for example to add side of lows on omni. But I overdo it with effects quite often. And then when I return to the recording after a while, I'm unpleasantly surprised.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: rocksuitcase on October 18, 2020, 10:17:01 AM
https://taperssection.com/index.php?topic=195541.msg2342957#msg2342957

Here is an OMT6 we did last year in an acoustically great room- The Egg in AlbanyNY
https://archive.org/details/jh50f72019-09-24.akgomt
Recording Info:
Source MDAUD:
ch1|2     AKGck22 omni spread 6 feet apart > Grace V2 >Tascam DR680|SD
ch3|4     AKG ck8 shotgun fwd 0'|AKGck61 cardioid rear 180' >Tascam DR680|SD
ch5|6     AKG c426 (Blumlein:fig8, 90) >V3 >HDP2 (24/48) >Tascam DR680|SD
Location: Row O center 70 feet from stacks about 5 feet up.
Transfer: SD >Audacity >CD WAV Editor >TLH >FLAC
Photos of the rig:
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on October 19, 2020, 12:45:37 AM
https://taperssection.com/index.php?topic=195541.msg2342957#msg2342957

Here is an OMT6 we did last year in an acoustically great room- The Egg in AlbanyNY
https://archive.org/details/jh50f72019-09-24.akgomt
Recording Info:
Source MDAUD:
ch1|2     AKGck22 omni spread 6 feet apart > Grace V2 >Tascam DR680|SD
ch3|4     AKG ck8 shotgun fwd 0'|AKGck61 cardioid rear 180' >Tascam DR680|SD
ch5|6     AKG c426 (Blumlein:fig8, 90) >V3 >HDP2 (24/48) >Tascam DR680|SD
Location: Row O center 70 feet from stacks about 5 feet up.
Transfer: SD >Audacity >CD WAV Editor >TLH >FLAC
Photos of the rig:

How much of the rear mic did you use in the final mix?  Looks like you're near the back wall so I'm curious what it was picking up.
Title: Crossing over or not
Post by: Gutbucket on October 19, 2020, 12:57:50 PM
There seems to be two basic mindsets with respect to combining the center and wide-spaced pairs (lets assume the wide-spaced pair are omnis). I'd like to discuss this a bit more.

The first is to use both full range.  The second is to low-pass the omnis, or to take that to the logical conclusion of setting up a cross-over where one pair "hands-over" to the other at the cross-over frequency.  For the most part in this post I'm primarily talking about those four channels.  it applies to additional channels as well but that's an unnecessary complication in this particular discussion.

>The full-range technique is simplest to implement, and produces complex interactions between the two pairs.
>The cross-over technique is more complicated to implement, and eliminates the complex interactions between the two pairs.

Lying somewhere between those opposing approaches are:
>Low-pass filtering the omnis alone.
>Using directional microphones in the center pair that feature a significantly reduced low frequency response beyond proximity effect range.
>Using EQ to shape one or both pairs with the intent of affecting the interaction of the pairs across various frequency ranges (as opposed to EQing for tonal correction or general sweetening).

The cross-over technique is attractive in a few ways, particularly from a theoretical perspective as it simplifies things by eliminating interaction between the two pairs outside of the cross-over region.  It's output can be thought of as a single stereo pair with different behaviors above and below the selected crossover point - coincident pair stereo behavior above and spaced pair stereo behavior below.  The crossover point and slopes might be determined by analytical factors such as sound location models of human hearing, the particular spacing used between the wide-pair, perhaps the intended stereo recording angle, etc.  Yet for the most part the practical approach is to play around with the crossover point while listening to determine what sounds best by ear.  Best results using this technique are found by careful tuning of the crossover such that the hand-off is seamless and natural sounding.  In a way it values preserving the ultimate coherence of the direct arriving sound from the stage (and PA if present) above other aspects of the recording.

The full-range technique is initially attractive in its simplicity.  I also find it attractive for how it seems to more naturally convey the ambient aspects of the recording environment.  The interactions it produces are something I value strongly as long as they are well behaved.  It helps convey more of what I'm personally looking for from OMT and is to my way of thinking, partly what makes OMT more than a "more advanced version of a single two channel stereo pair arrangement".  I do feel that for the interactions to work successfully, stronger constraints are placed on the physical arrangement of the microphones.   For one thing, the omnis need to be spaced sufficiently far apart to sufficiently decorrelate their higher frequency pickup with respect to each other and with respect to the signal they pickup in common with what the center pair is picking up.

The cross-over method might better accommodate an otherwise overly narrow spacing between omnis by eliminating conflicts introduced when combining two pairs placed too close to each other, yet not so close to be perfectly coincident.  It can be a way out of the all-or-nothing condition imposed by spaced omnis intended to be mixed with other pairs - the signals either need to have exactly the same phase-relationship (coincident placement) or spaced sufficiently far apart to sufficiently decorrelate the phase-relationship between them in the frequency range in question. ..or alternately, made directional and pointed in a different direction.

Allowing for more complex interaction is likely to be attractive to those who value the sensation of being present in the physical space in which the concert was performed more highly than the super precise imaging one gets from well-recorded studio material.  Crossing over completely is likely to be instinctively attractive to folks with studio recording or live sound mixing experience for whom the careful fitting together of multiple monophonic channels in a mix is standard practice.  A preference for the result using this method may reflect a subjective preference for "minimizing phasiness", and for ranking the coherence of direct arriving sound and pin-point imaging more highly than the portrayal of immersiveness and the sense of being in the performing space.

Given the range of subjective preference combined with the nature of the stereo playback illusion, neither approach need necessarily lay claim to being any "more correct" than the other.  Fortunately we can make the decision on which how to mix it with plenty of opportunity to listen to the difference.  With all this in mind we can setup the mics with a preferred arrangement in mind, which may end up getting modified by whatever constraints we are subjected to (realities of the recording situation, of the venue restrictions, of our mounting bar and support system and the mics we are using) and gain some ability to adapt to those changes by how we choose to mix it.

I mostly use the omnis full range, along with some EQ shaping. I tend to high-pass or more dramatically EQ the low end from the directional mics (perhaps due to wind-noise or whatever) before I low-pass the omnis.  In surround I use the decorrelated mids and highs from the wide omni pair to feed the surround channels, along with the rear facing mic(s) when they are present, while the extended bass from the omnis provides the LF information for the entire array.  In otherwords, I'm sometimes splitting up and using the full range of bass and highs from the omnis somewhat differently for surround playback verses in a 2ch mix, but in either case I'm still using the full range (EQ'd) response from them without discarding all of their high frequency content.  I suspect that one of the reasons I like retaining that HF spaced omni information in a 2-ch stereo mix as well is that it to my ear it helps convey some of what surround playback is so good at doing.  By all means, throw it out if you can't get to work right, at which point the LF portion alone remains a worthwhile improvement that needs no further justification for its inclusion.  But if I can arrange things so as to take good advantage of the HF spaced omni content as well, all the better.

Title: Crossing over or not
Post by: Gutbucket on October 19, 2020, 01:35:39 PM
Summarizing-

Pseudo-random phase relationships between channels can be beneficial or not.  With regards to "beneficial or not" some listeners may deem what others hear as being beneficial as being an "phasey mess", while others may deem a more strict phase-relationship as "flat, boring, and lacking a sense of space and dimentionality".  There is room between extremes to find whatever works best and sounds right to you, and there are a number of ways of managing the phase-interactions between channels with this in mind, both by way of the microphone setup and by way of how the resulting channels are treated and mixed.  The goal for me is an optimal combination of both coherent-phase direct-sound imaging and pseudo-random phase ambient-sound immersion.

We work within a large set of constraints.  I've worked to develop my OMT setup in such a was as to try and optimize the phase-interactions between channels via the physical arrangement of all the microphones in the array, which in turn probably gives me a bit more freedom in mixing and not needing to do things like applying low-pass to the omnis in comparison to a setup unable to achieve the same amount of omni spacing that may produce a better end result by low-passing them.  Do whatever sounds most-right given the constraints in which you are working, directed by your own preferences.  I'm not here to say "do it like I do", but rather, "consider these things" in an effort help everyone achieve the results they want.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: rocksuitcase on October 19, 2020, 03:29:47 PM
https://taperssection.com/index.php?topic=195541.msg2342957#msg2342957

Here is an OMT6 we did last year in an acoustically great room- The Egg in AlbanyNY
https://archive.org/details/jh50f72019-09-24.akgomt
Recording Info:
Source MDAUD:
ch1|2     AKGck22 omni spread 6 feet apart > Grace V2 >Tascam DR680|SD
ch3|4     AKG ck8 shotgun fwd 0'|AKGck61 cardioid rear 180' >Tascam DR680|SD
ch5|6     AKG c426 (Blumlein:fig8, 90) >V3 >HDP2 (24/48) >Tascam DR680|SD
Location: Row O center 70 feet from stacks about 5 feet up.
Transfer: SD >Audacity >CD WAV Editor >TLH >FLAC
Photos of the rig:

How much of the rear mic did you use in the final mix?  Looks like you're near the back wall so I'm curious what it was picking up.
I didn't take the exhaustive notes I usually do during mixdown, but iirc, I kept in the rear channel, but about -18dB down from the rest of the channels.
And in keeping with Lee's commenting on all of our mixing techniques, I can say, by the time I get to choose rear mic or not, or at what level, I've already processed outside channels as a stereo pair, levelling L/R. Then the inside (center/rear channels) get "mixed" in in by mono'ing each center channel (select track, select mono with Audacity) and then levelling it in relationship to the outside channels. In this case, I had three forward facing channels, the ck8 and the 426 fig 8' pair. So I had to "tread lightly" when combining them. On this recording I did not use a LPF, but did use EQ reducing 400Hz on down about 4-5 dB on the omnis.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on October 19, 2020, 04:11:22 PM
Rocksuitcase, thank you for your recording from Egg. It sounds great. Thank you also for sharing you mixing procedure.

Gutbucket, I really like what you wrote about lpf/hpf crossovers. My opinion is the same. I'm glad, now I'm sure I didn't listen in the wrong way, but that it depends on personal preferences and that one way may suit someone and the other way someone else.

I am using Raper and it is easy to setup crossover there. It is possible to link hpf and lpf and changing their crossover frequency by one slider. (If anyone is interested, I can write instructions on how to do it.) So the implementation is not limitation for me. But I just prefer full range mix for the reasons of sound, which Gutbucket explained.

There is something that is between full range and lpf/hpf crossover. It is "tilt eq". You can enhance the bass and suppress the treble on one track (omni) and do the opposite on the other (xy). You can also link two "tilt eq" in Reaper, so it is possible to sweep crossover frequency to see what is happening.
I love this. I don't use it in the final mix, but it is great that it shows how omni and xy contribute to the resulting sound. We just enhance /suppress a low/high of omni/xy. But everything still sounds together. It says a lot more than just turning omni/xy on/off.
It is useful for me because it shows the weaknesses of omni and xy in the final mix. And when I know the weak points, I can fix it by individual standard eq. (If you have no possibility to link a crossover frequency, the crossover can be set before and then only turn the two tilt eq on and off.)

Title: Re: Crossing over or not
Post by: heathen on October 19, 2020, 04:29:05 PM
With regards to "beneficial or not" some listeners may deem what others hear as being beneficial as being an "overly phasey mess", while others may deem a more strict phase-relationship as "flat, boring, and lacking a sense of space and dimentionality".  There is room between extremes to find whatever works best and sounds right to you, and there are a number of ways of managing the phase-interactions between channels with this in mind, both by way of the microphone setup and by way of how the resulting channels are treated and mixed. 

In the interest of defining the extremes, what configuration would represent the most strict phase-coherent relationship?  A coincident stereo setup like XY or mid-side?
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 19, 2020, 05:31:20 PM
^ Yes, sampling from only a single point in space using any coincident array.
That includes X/Y, M/S, Blumlein (which is just a sub category of those), Dual M/S, or ambisonic microphones.  They all ideally produce no phase differences between channels because they are derived from a single point in space.

A spaced pair of omnis crossed over to a coincident center pair produces phase differences only below the cross over point, and within the transition region of the crossover.  Below the crossover its the interaction between 2 points in space, in the transition region its the interaction between 3 points in space- the two omnis and the single center position shared by the coincident pair.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 19, 2020, 05:46:04 PM
There is something that is between full range and lpf/hpf crossover. It is "tilt eq". You can enhance the bass and suppress the treble on one track (omni) and do the opposite on the other (xy). You can also link two "tilt eq" in Reaper, so it is possible to sweep crossover frequency to see what is happening.
I love this. I don't use it in the final mix, but it is great that it shows how omni and xy contribute to the resulting sound. We just enhance /suppress a low/high of omni/xy. But everything still sounds together. It says a lot more than just turning omni/xy on/off.
It is useful for me because it shows the weaknesses of omni and xy in the final mix. And when I know the weak points, I can fix it by individual standard eq. (If you have no possibility to link a crossover frequency, the crossover can be set before and then only turn the two tilt eq on and off.)

I love tilt EQ!  If one thinks of EQ filters behaving more "musically" at low Q-factors, a tilt EQ might be considered a zero-Q filter.  Not sure of the mathematics of that, just extrapolating from the use of peak filters of higher and lower Q.  Tilt EQ is in a sense, sort of an ideal tone control.

The way you describe using complementary tilt filters on the omnis and the center X/Y pair is essentially the creation of a crossover with a transition region that spans the entire audible frequency range.  It would produce the most phase interaction between the two pairs at the center hinge-point of the tilt and gradually reduced interaction above and below that point.  I've not tried this but it appeals to me and sounds like a great application of the tool.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 19, 2020, 06:07:07 PM
Is it easy to to do this kind of inverse-function linking for other types of filters in Reaper?

I've posted in the past (not sure if in the OMT threads or elsewhere) about my wish for this type of real time inverse-function filtering as a basic functionality for mixing.  Reduce from this channel (or pair or group) whatever I am adding to this other channel (or pair or group) in an energy preserving way with respect to the output.

Applied to EQ- If both channels have equivalent energy across the same frequency ranges, but otherwise a different quality of content, this would allow for a single knob turn in deciding where the perfect balance lies rather than adding some here and cutting some there in an attempt at manually compensating so as to keep the overall output otherwise equal.  Would be especially useful for exploring what more complex EQ compensation curves in the trade off between channels.  I say basic functionality because I would use this for many things, including making level balancing between channel pairs easier.  Take for example deciding on the level of the rear-facing channel or pair in the mix since we were just talking about that.  I'd love to use a single control to essentially cross-fade between all channels without any rear channels and all channels including the rear channels, without the overall output level being changed.  Could be applied to any filtering applied across multiple channels,
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on October 20, 2020, 12:57:38 AM
There are two ways to link plugin parameters in Reaper. I use only the simple one. The simple way is that the linked plugins are all in one track. One track can have multiple stereo independent channels. It's the same as multiple tracks, but this way linked plugins are only under one track. I do this by sending stereo tracks omni, xy, rear pair to the main track with 3 independent stereo channels. Then I put required plugins on each stereo channel and link all their parameters. Output from the main track has no limit. You can freely send 3 independent stereo channels where you need. Or you can mix them straight there.
It is also possible to link plugins that are in different tracks (not channels), but it is complicated. To link plugins in one track with multiple channels is easy.

When linking parameters, scale [-100% + 100%] and offset [-100% + 100%] can be set. If you want an inverse link [scale -100%], the parameter should have symmetric range. It is possible to use the offset, but doesn't work for all cases. For example, I was not able to set inverse link for the parameters that have range [-120db + 6db]. For this case, I didn't find solution. I have not yet understood all in detail.

The next nice thing that is possible in Reaper is to link basic control buttons of tracks - solo, mute, volume, pan, width. You can make these links between any tracks, there are no restrictions. You can also make an inverse links e.g. mute/unmute.

So far, I haven't found an easy way to compensate the overall volume when mute/unmute track, e.g. "rear" track. I tried to set the rear track with a compensation track to compensate overall volume that had the opposite polarity than the main track. But it's complicated. For big changes, I had to re-tune the ratio of the rear track and the compensation track. And that was pretty annoying. Sends between tracks were also not clear.
The second solution is to make a compensation track with the same polarity as the main track. Initially, manually set the rear and compensation tracks to the same volume. Then link their volume control and set mute control as invert. When the rear track is switched on, the compensation track is switched off and vice versa. That could work. All that remains is to manage clearly and correctly the sends from the main track to the compensation track and back.

EDIT: I tried both methods. Both methods work well.

I don't know the terminology, I hope it's not confusing. If you are interested, I can find nice tutorial videos about this. Or I can create some templates.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: fireonshakedwnstreet on October 20, 2020, 08:43:55 AM
Fascinating discussion. I keep coming back to this thread again and again!

Anyway, I implemented the EQ advice that was graciously shared and am linking to an MP3 file of the entire recording: https://drive.google.com/file/d/1sHykMK-WD3l6FKt5TWQyYKeC86ugskUt/view?usp=sharing (https://drive.google.com/file/d/1sHykMK-WD3l6FKt5TWQyYKeC86ugskUt/view?usp=sharing)

EQ was as follows:
Split Omnis - +9b under 250 Hz/+9 db over 8000 Khz
XY Supers - Left channel panned to 30% left/ right channel panned to 70% right
Front/Rear Cards - Front panned slightly right of center

Mix and rendered in Audacity: omnis (-2); supers (-3); Front card (-3); Rear card (-8). Track amplified to -0.1.

Am I on the right track here? Thanks Team OMT
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on October 20, 2020, 09:52:31 AM
Thanks for recording. What is good to try is to compare the two version you have done. Load both recordings to Audacity and switch between them when playing. To compare it right it is necessarily to set the levels that both recordings sound equally loud. This is very important because different levels can influence us a lot. What sounds a little louder comes to us as being better.

Audacity is good. But if you like OMT, maybe it is good to try some another DAW. In most DAW, you can set up the operations you did in Audacity, all at once, not step by step. And you can change all parameters during playback, so you immediately hear how it affects the whole mix (or just the individual track, there are a lot of possibilities). And when you're happy with how it all sounds, you can render it into e.g. flac or mp3. This way you can also make different versions and compare them.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: fireonshakedwnstreet on October 20, 2020, 11:16:42 AM
Thanks kuba. I have played around in Reaper, but it honestly gives me a headache! I have the manual and am going to go through it during what is going to be a long break from taping. Audacity is sloooow but really easy to use.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 20, 2020, 12:56:00 PM
Kuba e- Good advice above. And thanks for the info on inverse linking parameters in Reaper. I may look into Reaper again just for that. I'm sure much has changed since I looked at an early version.

Fireon..- Will try and listen tonight with better headphones or speakers, but listening on the crappy Samsung in ears I have here at work right now (annoying because they need to be hand-held in place to work decently) and streaming the Morning Dew's through two browser tabs to compare, I hear the image well centered now, but I find myself missing the sense of width the previous version had.  This version seems overly center heavy.  I also preferred the tonality of the original in an overall sense, but difficult to really to judge tonality correctly on these 'phones, especially bass.  Yet in comparison something seems off, sort of like there is more mid-range predominance or a sort of can resonance sound.  Could be a side effect of less width..

XY Supers - Left channel panned to 30% left/ right channel panned to 70% right
^
I'd try keeping these as widely panned as possible. 

I'd try it a couple different ways:
1) Try it without any forward-facing center mic, balancing the image by panning the Left X/Y channel somewhat towards center, but leave the Right channel panned hard Right. 
2) Keep the X/Y pair fully hard-panned Left/Right and use panning of the forward-facing center mic to balance the image. 

Key variations on 2)
a) Try the center mic hard-panned right and slowly raise its level until the image is centered.  You may only need a little bit of it in this way to get the image centered. This is likely to retain maximum image width.
b) If you like more of the forward-facing center mic, increase width of the X/Y pair as described previously using a Mid/Side readjustment or stereo width controller to compensate for using more forward-facing center mic panned less hard to right.

My suspicion is that the variation in bold might work best in this case, and is simple to try. 

Otherwise, adjusting width of the X/Y pair (most likely increasing it significantly) by using a Mid/Side tool or stereo width controller is what I suggest for an X/Y center pair angled so as to Point At Stacks.  Here is the thinking behind that: We are using a coincident pair in the center for all the reason's previously discussed, so that means either an X/Y pair or a M/S pair there.  An X/Y pair in PAS is angled so as to maximize the pickup of direct sound from the PA (a good thing for this pair) by putting both mics directly on-axis with the PA.  However that translates to an overly narrow angle and image width, so we compensate for the narrow microphone angle by increasing the stereo width of the pair during mixing.  Does that make sense?  Using a Mid/Side pair instead of X/Y in the center requires conversion to X/y anyway, so its width adjustment is already a part of the working process.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: fireonshakedwnstreet on October 20, 2020, 01:39:05 PM
Thanks gut. Will give that a try!
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 20, 2020, 02:07:34 PM
Thinking about that a bit more, I now realize that mixing-wise it might be easier (and perhaps more enlightening) to mix an X/Y pair that needs width readjustment more like a Mid/Side center pair, using 3 mixer channels.

1) Use a Mid/Side tool to convert the PAS X/Y center pair to Mid/Side.  Put Mid on one channel.  Duplicate Side and put it on two channels. 
2) Bring up the omnis alone. Confirm they are relatively well balanced in terms of energy if not in stereo image.
3) Pan the Mid channel to center and bring it up to find a perceptually correct balance between the omnis and center.  Pan the center as necessary to correct any center image imbalance.
4) Pan one of the Side channels hard left.  Pan the other Side channel hard right and invert its polarity. Link the Side channel faders or manually keep them adjusted to the same level.
5) Now bring up the two Side channels together to increase width from the hard center.  Use as much as you need to find an optimal width blend between omnis and center pair. Play around with it.

The cool thing about this is that you balance omnis and mono center first, then add center width as necessary.  It might be easier to find the optimal blend of image width this way.  Its also enlightening to be able to mute the Side channels when you have additional stereo pairs in the mix.  You can also affect balance and centering of the Side information by intentionally not keeping the two Side channels at the same level. Once you find a Side balance that works best, link the Side faders or otherwise keep their relative level relationship the same as you play around with the amount of Side in the mix.

This provides you with two ways of adjusting center image balance- Panning the direct-arriving sound from the Mid channel, and panning the indirect-arriving Side information by way of the relationship between the two Side channel faders. Think of it as panning the center point, adjusting the width out to the left, and adjusting the width out to the right, all separately from each other.


I'm using three stereo pairs plus the center Mid/Side pair.  I typically keep the omnis hard-panned, my forward facing mid-spaced pair hard panned, and often the rear-facing pair hard panned.  Sometimes I pan the rear facing pair more toward center to get a more seamless ambience across the back, but they are at a lower level and that's more of a find tuning thing.  Typically the only thing that's not hard left or right is the center Mid channel. It's very interesting to be able to have the whole mix up and dialed in and mute and unmute the Side channel.  A lot of magic seems to come from the contribution of that figure 8 side channel.  Deriving Side channel from the X/Y pair should do the same, although with a PAS X/Y pair you will probably need increased fader level from it to achieve the same result.  If you need to amplify the Side channel more than the amount of travel your fader gives you that's ok.

Other than potentially using different amounts of ambient Side on the left and right, this is essentially the same as using a stereo width control and balancing the center and omnis with that control set to mono prior to increasing width to whatever works best.

Hope this makes sense.

Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on October 21, 2020, 12:58:56 AM
I understand you Fireon. I also started with Audacity and then I moved to Reaper. Beginnings are hard because it's a slightly different philosophy than how to work in Audacity. Patience is needed. Maybe do the main things in Audacity and gradually,when you have the time, try some simple things in the Reaper. Small step by small step. I'm sure there are other DAW's, maybe you could find one that would suit you. If you can move from Audacity, it'll make it easier for you to work with OMT in the future.

Gutbucket, if you need anything with the Reaper, I'd be happy to advise on what I know.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 21, 2020, 09:25:12 AM
Thanks.  Will need to get my editing setup back in action first, then I'll take a deeper look at Reaper.  Currently using Samplitude.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 21, 2020, 01:18:19 PM
Really enjoying listening to that Jimmy Herring Egg recording again, big thanks Rock' and Kind'.

A more advanced post on OMT mixing today-
When I keep myself in analytical mode when listening to high quality recordings like that one where things are working well (acknowledging that what denotes "high quality" to me is the ease in which I can let myself switch out of that mode and get carried away by the music), one of the more nuanced things I tend to notice are the differences between the portrayal of the quieter, less-dense parts and the louder, denser portions.  That leads me to thinking about why they are different, how I might manage them differently, and how I might arrange implementation of that in an automated way. 

It's not so much the change in dynamics as experienced through the recording (which can also be a factor of course), rather I've long noticed quieter/less-dense parts sound best with more emphasis on the ambience than loud/dense parts which sometimes tend to get thick and cluttered, loosing dimensionality.  I suspect this is likely the acoustic behavior of the room as experienced at the recording position as the room gets increasingly loaded with acoustic energy which is no longer being sufficiently dissipated, and that is being faithfully translated through the recording.  Three things from my experience inform this view: Listening of various bands/ensembles in specific rooms - particularly amplified material performed in rooms designed for acoustic music; listening to my own recordings in surround and trying to decide on an optimal level of the surround channels - generally deciding it should vary along with the density and intensity of the music; and the difference when mixing to 2 channels - where it should also vary, but needs to be adjusted with more careful consideration, and the overall amount and its dynamic variability is more critical, for somewhat different reasons.  This balance between Direct and Ambient sound is one of the two things (and pretty much the only two IME) that beg to be treated somewhat differently for 2-channel stereo verses multichannel surround stereo, the other being how best to manage 3 front playback channels instead of 2.

For somethings I've been willing to put the time into I've used manually applied automated volume envelopes on the rear-facing channel(s).  I haven't but could do the same with some or all of the content from the omnis as well if things get over boomy when it gets loud.  I've not yet played around extensively with trying to further automate it using gentle program compression but that would be a much easier way to do it. Something like parallel compression on the ambient stuff so it automatically contributes more during the lower level parts and effectively gets backed off during the louder parts.

I have tried applying some gentle straight-compression to the rear facing channels and couldn't really get that to work in the way I wanted (that being parallel only in the sense of the main channels not being compressed at all), and should probably revisit this with proper parallel compression on the ambient channels as that tends to sound more transparent to me.

Interestingly I wonder if applied to the omnis it might be good to use a somewhat differently shaped detection signal.  Reducing the omnis when the bottom end gets over thick, and reducing the rear facing channels when the ambient reflections get over-dense.

This is complicated stuff, don't worry about attempting to apply anything like this until you feel fully confident in all other aspects of mixing these OMT recordings.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on October 25, 2020, 10:02:28 AM
This is interesting. I recently listened to some Bob Dylan's 40-year-old recordings, some sound fantastic. Even recordings of semi-electric music that were made with cheap microphones sound very good. In contrast, audience recordings of very loud music made with cheap microphones are usually bad. I also guess it has to do with the acoustic of the room. Because the differences between a cheap and an expensive microphone decrease again when recording onstage. I thought that more expensive microphones could capture more precise details, and probably those details are important in an audience recording in a room with bad acoustic. It seems to me that those who record folk and country have a big advantage. Classical music does not forgive any inaccuracy, and loud amplified music has very few details.

I tried several times, when I had a recording where there was a bad sound at the beginning and over time the sound engineer improved it, to choose a different ratio of omni and xy in the first and second part.

It's a good idea trying to reduce the omni or the rear channels for louder parts of the recording.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: heathen on October 25, 2020, 11:41:53 AM
Never forget the paramount importance of location. Mediocre mics in the best spot will walk all over the best mics in a mediocre spot.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on October 25, 2020, 11:48:28 AM
I think most times I actually end up using everything I put up.  The real challenge is in the level tweaking, especially challenging when many secondary spatial elements are 15-20dB down relative to the mains, and possibly heavily filtered. You can mute/unmute and not hear an obvious difference, so it takes a long period of deep comparative listening to decide if 1) it’s worth keeping 2) should that stuff go up 1dB, or down?  Etc.  Then listen on a bunch of different systems; that’s where I’m most likely to discard an element entirely, like filtered spot shotguns for example. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on October 26, 2020, 09:53:52 AM
Heaten, you are right, the location is the most important. But Besides, I have a feeling, there is a bigger chance that the audience recording will turn out well when, for example, jazz is recorded compared to loud rock.

EmRR, you described it exactly. I also sometimes listen for a long time before deciding whether to use the rear channel in the mix. These are very delicate things.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on October 26, 2020, 11:11:06 AM
What EmRR mentions above rings true for me.  Most of the time I also tend to use all of the channels I've recorded and careful adjustment of relative levels is the most critical adjustment.  I do think its important to emphasize that its OK to not use all recorded channels, and to try the option when exploring to determine what works best in the mix. Also to listen long enough to sort of get out of one's head and really get a deep feel for what is best.  Something I've noticed and find quite interesting is that both long-term listening and the first initial few seconds of listening can be especially revealing of certain things I otherwise quickly acclimate to and may tend to overlook when working on a mix.

Over the weekend I pulled out the rig and was listening to one of the last recordings I made prior to the shutdown.  It was at an outdoor amphitheater, and as such avoids a lot of the overloaded room issues when things get cranking. Interestingly what I wished to automate in this case was not the level of the rear-facing channels but the level of the Side channel of the center M/S pair.  Partly because I'm listening back directly from the F8, which provides playback level and pan control for all channels except those routed through M/S>L/R decoding, which can only be muted or soloed.  That means I build the mix around the fixed level of the center Mid channel, and after all other channels are balanced well against that, I play with switching the Side channel in and out.  Remember that I'm using an LCR near-spaced arrangement of supercards, the center of which is serves as the Mid of the M/S pair, so there is already directional stereo information from the 3 LCR arrangement.  The full 7 channel mix with the Side channel muted is nice and solid and dimensional as it is.  Still, switching in the Side channel adds a whole 'nother layer of dimension. Unfortunately I can't vary the level of Side and its a bit too much at some points.  Ideally I'd lower the Side level and suspect I would find a setting that works everywhere.. but the reason I'm posting this is that given the Side level and resulting M/S ratio I was stuck with I found myself preferring both with Side and without Side at different points within in the recording and at different points within my listening time.  Often upon switching it in while listening the otherwise somewhat-excessive Side is attractive, then at some point it strikes me as too much, especially upon long term listening.  Often that corresponds with things getting more dense, complex and louder.  But I also noticed it when stepping away long enough for my acoustic memory to "reset" upon coming back again.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: kuba e on October 27, 2020, 08:23:19 AM
Thanks Gutbucket, that's a good inspiration. I will focus on quiete and louder passages and try different settings.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on November 06, 2020, 11:54:43 AM
This is interesting. I recently listened to some Bob Dylan's 40-year-old recordings, some sound fantastic. Even recordings of semi-electric music that were made with cheap microphones sound very good. In contrast, audience recordings of very loud music made with cheap microphones are usually bad. I also guess it has to do with the acoustic of the room. Because the differences between a cheap and an expensive microphone decrease again when recording onstage. I thought that more expensive microphones could capture more precise details, and probably those details are important in an audience recording in a room with bad acoustic.

Coming back to this, I think it hinges on the naturalness and good behavior of the microphone's off-axis sensitivity and performance being far more critical in a live audience perspective recording, due to that representing such an inseparably large portion of the resulting recording.  In the studio, isolation and extreme off-axis rejection is more possible, easier to achieve, and expected, and whatever ambience it has is more purposefully created.  This is reflected in the particular attributes of high quality "taper" mics.  And by extension, I see the value of OMT hinging largely on improving the quality of off-axis pickup still further with regards to how we are able to manage and manipulate it in an overall sense.
Title: Revisiting a little OMT mixing trick I really like and intend to explore further
Post by: Gutbucket on February 17, 2021, 06:25:58 PM
I intended to get my editing computer back in operation and get down to mixing past recordings over the past year.. but, well same old story.

Anyway, I found an old installation of Audacity on my work computer last week and pulled up a classical recording I'd made prior to shutdown, for a much needed listen and a grin.  I used no EQ at all, which is clunky in Audacity (this version at least) because it is not real-time adjustable. So I decided to use simple channel mixing only and see how good I could get it.

This recording was made using my simpler four channel OMT rig using 4 x DPA 4060s.  The raw recording is in a LRCB (B = back) format using one microphone mounted centrally on each side of an acoustically absorbent rectangular baffle measuring approximately ~20" wide x ~4"-7" thick.  You might think of the arrangement as being somewhat similar to mixing a pair of spaced omnis with a front/back oriented pair of directional mics in the center.


Anyway, I brought in the L/R pair and level balanced those two channels. 
Brought in the C/B pair and split it into two mono tracks, panned the Center channel mono track to center and level balanced that against the L/R pair. 
Good.

I then panned the mono back channel to center and brought it up to taste.
As usual, adding some rear facing (B) channel improved on the LCR mix alone.

Taking it a step further.. and the reason for this post-
I then copied the Back channel to a second track, inverted polarity on the copy, and combined straight and polarity inverted channels to a stereo track again.
This was essentially treating the rear-facing channel like the Side channel of a M/S pair, except instead of a side-facing fig-8 coincident with C as Mid, it is a rear facing baffled omni.
I check it by soloing B+/B-.. and yep, it sounds much like a polarity inverted pair or a Side fig-8.

I un-mute the other 3 channels, bring the +B/-B fader back up and wow.  Such ambient width and dimension. So much better than mono B panned center.
Really good.

I mute the L/R pair, soloing the essentially M/S'ed C/B pair alone.
Not bad at all.  Not as much missing as I expected. Great clarity, depth and dimension.  No discrete L/R imaging, but it takes some listening to hear that the violins are no longer positioned left and cello and bass positioned right behind the up front piano dominating the center, instead the instruments that are further away become more diffuse, reverberant and enveloping, with a lush width complementing the clear center, yet without discrete imaging.

I do the opposite and solo the L/R pair.
I hear L/R imaging again, but if I had to choose one or the other I think I'd prefer the C/B alone.  It lacks directional imaging but has better clarity with a more engaging reverberant width and depth at the same time.

I go back to the full mix.
Yes, this is the full ticket, the complete package.
I play a bit with fine tuning the balance trade off between L/R and the now stereoized B (stereoized only in combination with the other channels).
It's best getting L/C/R balanced first for imaging, then bringing up +B/-B for depth, reverberant ambience, and naturally enveloping audience applause.

The caveat? Bringing up +B/-B begins to cancel out some low-end on the polarity inverted side, skewing balance in the low end.
I make a slight adjustment and bring up R a couple dB to compensate.  Not perfect, but OK

The better fix?   Instead of polarity inverting one copy of B, use the Voxengo PHA-979 stereo phase rotation VST to modify phase of one copy of B by +90° and the other by -90°.  This will keep low-frequency cancellation symmetrical.  Might also try some slight time-shifting of B, either using the delaying function in PHA-979 or via the multi-track editor itself.  PHA-979 is typically used for distance and phase alignment of drumkit mics, and making low frequency phase corrections.  There may be others, but I know of no other plugin with the same direct functionality. 


Additional potential benefit? This kind of symmetrical phase rotation is the basic operation a matrix surround encoder does with surround channel information when creating a 2ch LtRt output.  When played back through a matrix decoder, the B channel information will be routed to the surrounds.  Would need to play with it to make sure the levels end up right played back that way as well as in 2channel, and sure, matrix surround is no longer of much interest to many these days, but this is a cool additional benefit with no additional cost or detriment.  Although it has long been interesting to me I don't really wish to emphasize this last point, as I am mostly just enamored with how well this technique works as a mixing technique for OMT recordings intended for traditional stereo playback.  Yes, I've speculated about this technique previously in these threads, but its time to bring it back to focus again because it's just plain better IMO.  Rocksuitcase, what enlightenment might you provide from your past experience with the surround encoder/decoder you once were involved with developing and selling decades back?
Title: Re: Revisiting a little OMT mixing trick I really like and intend to explore further
Post by: EmRR on February 17, 2021, 07:39:20 PM
Instead of polarity inverting one copy of B, use the Voxengo PHA-979 stereo phase rotation VST to modify phase of one copy of B by +90° and the other by -90°.  This will keep low-frequency cancellation symmetrical.  Might also try some slight time-shifting of B, either using the delaying function in PHA-979 or via the multi-track editor itself.  PHA-979 is typically used for distance and phase alignment of drumkit mics, and making low frequency phase corrections.  There may be others, but I know of no other plugin with the same direct functionality. 

I need to play with that more, and consider applying it in BPF/HPF/LPF additive scenarios too.  Izotope RX has a phase rotation tool that can also be set to 'suggest' best rotation, if that is applicable. 
Title: Re: Revisiting a little OMT mixing trick I really like and intend to explore further
Post by: rocksuitcase on February 18, 2021, 12:45:48 PM


Taking it a step further.. and the reason for this post-
I then copied the Back channel to a second track, inverted polarity on the copy, and combined straight and polarity inverted channels to a stereo track again.
This was essentially treating the rear-facing channel like the Side channel of a M/S pair, except instead of a side-facing fig-8 coincident with C as Mid, it is a rear facing baffled omni.
I check it by soloing B+/B-.. and yep, it sounds much like a polarity inverted pair or a Side fig-8.

I go back to the full mix.
Yes, this is the full ticket, the complete package.
I play a bit with fine tuning the balance trade off between L/R and the now stereoized B (stereoized only in combination with the other channels).
It's best getting L/C/R balanced first for imaging, then bringing up +B/-B for depth, reverberant ambience, and naturally enveloping audience applause.

The caveat? Bringing up +B/-B begins to cancel out some low-end on the polarity inverted side, skewing balance in the low end.
I make a slight adjustment and bring up R a couple dB to compensate.  Not perfect, but OK

The better fix?   Instead of polarity inverting one copy of B, use the Voxengo PHA-979 stereo phase rotation VST to modify phase of one copy of B by +90° and the other by -90°.  This will keep low-frequency cancellation symmetrical.  Might also try some slight time-shifting of B, either using the delaying function in PHA-979 or via the multi-track editor itself.  PHA-979 is typically used for distance and phase alignment of drumkit mics, and making low frequency phase corrections.  There may be others, but I know of no other plugin with the same direct functionality.


Additional potential benefit? This kind of symmetrical phase rotation is the basic operation a matrix surround encoder does with surround channel information when creating a 2ch LtRt output.  When played back through a matrix decoder, the B channel information will be routed to the surrounds.  Would need to play with it to make sure the levels end up right played back that way as well as in 2channel, and sure, matrix surround is no longer of much interest to many these days, but this is a cool additional benefit with no additional cost or detriment.  Although it has long been interesting to me I don't really wish to emphasize this last point, as I am mostly just enamored with how well this technique works as a mixing technique for OMT recordings intended for traditional stereo playback.  Yes, I've speculated about this technique previously in these threads, but its time to bring it back to focus again because it's just plain better IMO.  Rocksuitcase, what enlightenment might you provide from your past experience with the surround encoder/decoder you once were involved with developing and selling decades back?
well, I've been out of the theoretical mathematics biz for some time, however, I will add that you have a solid theory regarding the +B/-B signal. We found that when attempting to use phase shifting to "stretch" the time of arrival, if you place that signal at the listeners rear (180') or directly in front (0') you could achieve a psychoacoustically significant illusion such that the brain/ears will hear added dimensionality. Again, we were analog only, we knew the time/phase shifting wasn't "3D" but presented it in our AES papers and patents as "2.5D". i.e. NOT a full three dimensional soundscape, but closer than L/R only.

Toward your mathematics- I would add that we found placing the 4 speakers in a LCR with one centered rear and putting the +B portion in the C speaker, then the -B signal in the rear speaker created the best 3 dimensional illusion. (as compared with 1 or 2 speakers on the side or rear corners) This prefernce was the result of human subject testing at Syracuse University in a very thorough set of studies aimed at determining what the brain prefers in terms of multi dimensionality and also the sonic quality of different materials of capacitors and resistors. A large majority of listeners preferred the LCR + R as opposed to four corners or 2.5 setups. We posited that because of the use of what you are terming +B/-B signals derived by our algorithms. (which later were stolen/used by Yamaha in their early 2 channel surround simulator circuits.)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on February 18, 2021, 06:51:24 PM
^ Very interesting and thanks so much. I have some questions to clarify my understanding of what you posted above that I'll get together later when I have more time.  I'm more curious than ever about the details of that whole thing and would love to be able to pick your brain about it in person.


I need to play with that more, and consider applying it in BPF/HPF/LPF additive scenarios too.

With regards to phase alignment (the primary application of that PHA-979 plugin), it would be applicable to the range of frequencies that are phase-correlated between channels, so the spacing between any two pairs of channels would determine the corner frequency below which it might be useful for that.  For coincident pairs that would be a rather high frequency.  Above that corner frequency the phase is essentially random, so phase rotation should have little if any effect.  Can check where that occurs with a correlation meter.

For doing the "more advanced polarity inversion split-phase" +/-90° thing it applies to the entire audible frequency range if applied to identical copy.

I wonder if the Izotope RX phase rotation tool is doing the same thing by rotating phase across all frequencies by the same amount. 

Link to the PHA-979 plugin web page- https://www.voxengo.com/product/pha979/

From the explanatory PDF found there-
"Phase shifting process of this plug-in does not skew the phase relationship within the
signal being processed, the phase response is linear across the whole frequency range
(this is achieved via FIR filtering). [..snip..] The only drawback of PHA-979’s
phase shifting process is a power spectrum roll-off below 20 Hz and above 20 kHz,
which gets stronger as the phase shift approaches 90 degrees."


Title: Re: Oddball microphone technique (OMT) - part 3
Post by: hugh on February 19, 2021, 10:54:11 AM
Love the discussion of phase shift for dimensionality.  Playing with Ambisonic mixdowns, the pure Blumlein figure-8 stereo mixes have plenty of "precision" but don't seem to give a very enveloping feel.  But I've discovered that if you take the "W" channel (i.e. an omni), then add -24dB of (W with 90-degree phase shift) to Left and -24dB of (W with -90 degree phase shift) to Right, the three-dimensionality really pops.  You only need a tiny amount of this level to make a difference, it can be 25 to 30dB down.

I don't have a theoretical background to tell *why* this works or whether it's justifiable by theory :)
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on February 19, 2021, 12:06:35 PM
Welcome to the discussion hugh!  That's interesting.  I'll try that with some of my Ambisonic recordings once I get my editing computer back in action.  When I was using the TetraMic I often used pair of spaced omnis flanking it as a way of achieving increased envelopment, sense of openness and space.  The two approaches may be similar in terms of perception.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on February 19, 2021, 12:20:08 PM
Yeah that sounds like a potentially great option for times lacking spaced flankers.  Will check that out, I've got a number of things I did with native B format and AB omni in which the W and the spaced are all the same omni type, should make for a tight comparison. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: jcable77 on April 14, 2021, 12:30:28 PM
GB, any positives or negatives on running maybe two split 10' M/S's, or M/S with split omni's on stage? Been thinking about trying these lately.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on April 14, 2021, 04:12:04 PM
M/S in the center + split omnis to either side has worked well on stage for me a bunch of times.  It's a quintessential 4-channel OMT setup as far as I'm concerned, working well both on stage and from the audience for me.

Somewhere I have a Charlie Hunter recording I made way back when using the TetraMic in the center between 4 split omnis.  It was the very first time I ran the TetraMic, so I retained the four omnis I had already planned on using.  I recorded them to separate recorders and remember playing around with both to compare, but never synced them up and only used the 4 omnis in the mixdown I provided to a video taper, then never went back to revisit possible combination of the two.  I should go back and dig that up.

Two split M/S pairs is an interesting approach I've not tried.  I have read of its use by someone for live classical recording - reportedly being particularly useful when there is a center isle that cannot be blocked with a centrally placed stand.  That's probably when I'd consider it instead of having something in the center.  As I recall, the mixing was described as panning the outermost channels from each pair hard Left/Right, with the inside channels from each pair being summed and panned center.  A split M/S pair using omni Mids is sort of a logical extension of a pair of split omnis alone, and should provide additional flexibility afterward.  I think how well it might work may hinge on how well the inner-facing channels sum, which is sort of a mono-compatibility question.   Might have to just give it a try and see.  If you are able to get a soundboard feed you will be better protected from potential "hole in the middle" if the summing of the inner-facing channels doesn't work out well.

I've only run twin M/S pairs once, but they were front and rear-facing MS pairs between spaced omnis, done on a whim one day at a fest by adding coincident 8's to the center front/rear facing directionals I already had in place. I don't think I ever got around to listening to the rear facing pair, recorded to a separate recorder.  I should dig that up too.  I went on to modify my regular setup by retaining the front facing M/S pair, yet went with a near-spaced rear-pacing pair.  However, I've recently been thinking about that again as a way of streamlining what I have aloft while retaining stereo rear-facing pickup of ambience/audience/room. 
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: jcable77 on April 14, 2021, 04:46:44 PM
Thats kind of what I was thinking with the two m/s's, pan outers far left and right, while lightly panning the inner sides. With omni mid's, I feel like it could give a real nice wide stereo image that could be fun to play around with. The other option using 4022's as mid's, they seem to have, at least to my ears, almost a subcard off axis response. Not as directional as other cards Ive used. Going to give both a try soon and see what I come up with
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: Gutbucket on April 14, 2021, 05:26:22 PM
Please let me know how it goes.  I'd try various ways of panning the inner facing channels.  Both panned center is one obvious thing to try, but also try them panned part-way to their own side, as well as part-way to the opposite sides.  Also, depending on the arrangement of sources on stage, it might actually work best with some sort of asymmetric panning arrangement on those inward facing channels.
Title: Re: Oddball microphone technique (OMT) - part 3
Post by: EmRR on April 14, 2021, 08:06:20 PM
Don’t think I’ve tried 2 MS sets like this, I see a lot of potential problems but I can’t say they are real.  There’s likely a spot it works perfectly, finding it is a different story. 

I tend to to some variation of MS with AB omni most times. Should work well at edge of stage.