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Author Topic: Oddball microphone technique (OMT) - part 3  (Read 21859 times)

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Offline heathen

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Re: Oddball microphone technique (OMT) - part 3
« Reply #180 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://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?
Mics: AT4050ST | AT4031 | AT853 (C/SC) | Line Audio CM3 | Sennheiser e614 | Sennheiser MKE2 | DPA 4061 | CA-14 omni Pres: CA9200 | DPA d:vice Decks: Zoom F8 | Roland R-05

Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 3
« Reply #181 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://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.
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 3
« Reply #182 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.
« Last Edit: October 14, 2020, 01:29:19 PM by Gutbucket »
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline fireonshakedwnstreet

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Re: Oddball microphone technique (OMT) - part 3
« Reply #183 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?
Mics: AT853Rx (cards); Nakamichi CM 300s (CP-1/CP-2); Samson CO2s; AT ATM41-HE
Recorders: Tascam DR-70D; Tascam DR-40
Pre: Edirol UA-5( BMp2+)
Recordings: https://archive.org/search.php?query=taper%3A%22David+Perez%22
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Offline fireonshakedwnstreet

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Re: Oddball microphone technique (OMT) - part 3
« Reply #184 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.
Mics: AT853Rx (cards); Nakamichi CM 300s (CP-1/CP-2); Samson CO2s; AT ATM41-HE
Recorders: Tascam DR-70D; Tascam DR-40
Pre: Edirol UA-5( BMp2+)
Recordings: https://archive.org/search.php?query=taper%3A%22David+Perez%22
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Offline heathen

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Re: Oddball microphone technique (OMT) - part 3
« Reply #185 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 :)
Mics: AT4050ST | AT4031 | AT853 (C/SC) | Line Audio CM3 | Sennheiser e614 | Sennheiser MKE2 | DPA 4061 | CA-14 omni Pres: CA9200 | DPA d:vice Decks: Zoom F8 | Roland R-05

Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 3
« Reply #186 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.
« Last Edit: October 15, 2020, 11:16:18 AM by Gutbucket »
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline fireonshakedwnstreet

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Re: Oddball microphone technique (OMT) - part 3
« Reply #187 on: October 14, 2020, 04:22:52 PM »
Thanks gentlemen for your detailed and very informative responses. Definitely have a plan of attack now!
Mics: AT853Rx (cards); Nakamichi CM 300s (CP-1/CP-2); Samson CO2s; AT ATM41-HE
Recorders: Tascam DR-70D; Tascam DR-40
Pre: Edirol UA-5( BMp2+)
Recordings: https://archive.org/search.php?query=taper%3A%22David+Perez%22
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Offline heathen

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Re: Oddball microphone technique (OMT) - part 3
« Reply #188 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.)
Mics: AT4050ST | AT4031 | AT853 (C/SC) | Line Audio CM3 | Sennheiser e614 | Sennheiser MKE2 | DPA 4061 | CA-14 omni Pres: CA9200 | DPA d:vice Decks: Zoom F8 | Roland R-05

Offline EmRR

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Re: Oddball microphone technique (OMT) - part 3
« Reply #189 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. 
Mics: DPA 4060 w/MPS 6030 PSU/DAD6001/DAD4099, Neumann KM 131, KMR 81i, Oktava MK 012, Sennheiser MKH 105, MKH 20, MKH 30, MKH 40, MKH 800 TWIN, lots of other studio appropriate choices
Recorders: Zoom F8n, Sony MZ-R50, portable MOTU based multitrack DAW for client work

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Re: Oddball microphone technique (OMT) - part 3
« Reply #190 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.
music IS love

When you get confused, listen to the music play!

Mics:         AKG460|CK61|CK1|CK3|CK8|Beyer M 201E|DPA 4060 SK
Recorders:Marantz PMD661 OADE Concert mod; Tascam DR680 MKI

Offline kuba e

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Re: Oddball microphone technique (OMT) - part 3
« Reply #191 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.
« Last Edit: October 15, 2020, 06:26:43 PM by kuba e »

Offline rocksuitcase

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Re: Oddball microphone technique (OMT) - part 3
« Reply #192 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:
« Last Edit: October 18, 2020, 10:19:49 AM by rocksuitcase »
music IS love

When you get confused, listen to the music play!

Mics:         AKG460|CK61|CK1|CK3|CK8|Beyer M 201E|DPA 4060 SK
Recorders:Marantz PMD661 OADE Concert mod; Tascam DR680 MKI

Offline heathen

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Re: Oddball microphone technique (OMT) - part 3
« Reply #193 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.
Mics: AT4050ST | AT4031 | AT853 (C/SC) | Line Audio CM3 | Sennheiser e614 | Sennheiser MKE2 | DPA 4061 | CA-14 omni Pres: CA9200 | DPA d:vice Decks: Zoom F8 | Roland R-05

Offline Gutbucket

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Crossing over or not
« Reply #194 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.

« Last Edit: October 19, 2020, 05:03:53 PM by Gutbucket »
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