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Author Topic: Oddball microphone technique (OMT) - part 2  (Read 9963 times)

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Offline rocksuitcase

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Re: Oddball microphone technique (OMT) - part 2
« Reply #105 on: May 18, 2018, 05:56:28 PM »
The XY pair on their own, though, was just too narrow of an image for my taste so I kept the omnis in the mix.

That's a good indication that you are doing OMT right!  Sort of like the inherent balance of a three leg stool.

I didn't listen to the entire recordings, but of what I did I preferred the portrayal of the audience reaction in yours.  More open, natural, less muffled, more spatially correct to my ear.  That's not necessarily with respect to the level balance of the audience, but at least for what I listened to the balance was in no way unacceptable.
I keep marking this thread unread all day today as I wish to comment on that sentence heathen, but am moving so fast today- so briefly- the OMT mix uses the decorrelation aspect of the theory which makes the stereo illusion seem more natural. the psychoacoustic result, to my ears, is random audience noises such as talking or beer bottle drops are de-emphasized in an OMT mix when compared to the straight omni or straight center pair (all other things relative of course).
« Last Edit: May 19, 2018, 10:57:43 AM by rocksuitcase »
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Offline dactylus

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Re: Oddball microphone technique (OMT) - part 2
« Reply #106 on: May 19, 2018, 09:20:58 AM »
I found the comparison of onstage DPA 4006a omnis vs onstage DPA 4015c wide-cards interesting too.  One recording was made on 5/10 and the other on 5/11.  Same band, same taper.  I was very surprised at how much more I liked the omni recording vs  the subcards.

Can you describe what it is you like so much more about the omni recording?

^ I enjoyed both of the recordings but I was sucked into the omni recording by the same strengths of this particular omni pull that you mentioned earlier.  The depth and fullness of the low end really grabbed me and I enjoyed the overall immersive feeling that the omni recording gave me.  The subcards were very powerful in their own right, crisp, clear and in your face, but in this case I enjoyed the total omni effect!




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Offline scottsch3

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Re: Oddball microphone technique (OMT) - part 2
« Reply #107 on: May 19, 2018, 05:37:39 PM »
FWIW I'm pretty sure Scott ran both omnis and subcards on 5/11.  I definitely remember seeing two pairs of mics on the stand.  I have no idea how to get in touch with him (met him for the first time that night), but maybe someone who does could cajole him into posting his other 5/11 recording for you guys...?

https://archive.org/details/gm2018-05-11.dpa4015c.flac16

Here is the 4015 source if it helps to keep the conversation moving along. It’s not going to be an accurate comp since I used the Portico in front of the 788 but the relative soundstage of the recording shouldn't be affected.
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Offline dactylus

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Re: Oddball microphone technique (OMT) - part 2
« Reply #108 on: May 20, 2018, 09:31:30 AM »
^Thanks Scott.  Did you enable the "silk" option on the 5012 for the 4015 source linked to above??
« Last Edit: May 20, 2018, 12:50:29 PM by dactylus »
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Offline goodcooker

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Re: Oddball microphone technique (OMT) - part 2
« Reply #109 on: May 21, 2018, 12:56:56 PM »
^Thanks Scott.  Did you enable the "silk" option on the 5012 for the 4015 source linked to above??

mmmmmnh, Silk.
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Offline djphrayz

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Re: Oddball microphone technique (OMT) - part 2
« Reply #110 on: June 26, 2018, 02:54:46 PM »
From previous thread https://taperssection.com/index.php?topic=96009.msg2250985#msg2250985


Quote from: Gutbucket
Here are a few tricks to maximize the spacing you can get with whatever bar you are using-
Point the omnis sideways, each facing away from the other.  You can probably gain a few inches additional spacing at minimum by using the length of the mic bodies and their position in the mounts to extend the capsules a bit further out to either side.

Would this omni configuration still be accurately documented as A-B?  Or is there another name for this configuration with the capsule ends pointed 180 degrees from one another?
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Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 2
« Reply #111 on: June 26, 2018, 03:48:17 PM »
Yes. "A-B" describes the omni pair, regardless of the angular orientation of the microphones.  The direction they point is more of a detail.  Pointing them outwards can help get a bit more spacing than you could otherwise, as well as increase the highest frequency stereo difference a bit if the omnis are somewhat directional.  Pointing them upwards instead of forward can act as tone control and reduce the high-frequency pickup of the main sound a bit.  Pointing them backwards maximizes the ambient and audience high frequency cues rather than those of the main sound, and maximally differentiates pickup in comparison to the forward facing center mic(s).

Play around with different orientations to see what works best in the mix with your center mic(s).  This is probably where different mics behave differently enough that a taper may have different preferences for what direction the omnis are pointed based upon personal preference and the gear used.  It can be somewhat subtle.  With really tiny omnis the effect of angular orientation will be insignificant, unless some kind of attachment is used to intentionally make them not tiny.
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Offline heathen

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Re: Oddball microphone technique (OMT) - part 2
« Reply #112 on: July 16, 2018, 01:48:31 PM »
I've been thinking a bit about using a baffle with omnis in situations where really wide spacing isn't feasible.  One of the approaches I've been thinking about (and to be clear, I'm not claiming this is an original idea), is two small-ish circular baffles with some space between them and with the omnis mounted either flush or nearly flush with the surface of each baffle.  The general idea being something like this, but without the incorporated electronics and fake ears: https://3diosound.com/products/free-space-binaural-microphone

Right now my idea is a couple of these ( https://www.ikea.com/us/en/catalog/products/87077700/ ) with a dowel or some tubing between them.  The dowel/tubing could then be held in a Rycote INV-style shock mount.

So my first question is whether the cork of those hot pads would be sufficient to block sound and make an effective baffle?  If not, what could I do to make them better (or, what could fill that role better)?  Also, any ideas about attaching the baffles to the central connector, particularly in a way that they can be taken apart for easier storage in a bag?

Edit: Another idea for the baffles, which would be much smaller and thus easier to transport, is some wooden coasters.  Again, one on each end of the connecting dowel or tube of some sort.
« Last Edit: July 16, 2018, 02:17:00 PM by heathen »
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Offline goodcooker

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Re: Oddball microphone technique (OMT) - part 2
« Reply #113 on: July 16, 2018, 02:59:41 PM »
I've been thinking a bit about using a baffle with omnis in situations where really wide spacing isn't feasible.  One of the approaches I've been thinking about (and to be clear, I'm not claiming this is an original idea), is two small-ish circular baffles with some space between them and with the omnis mounted either flush or nearly flush with the surface of each baffle.  The general idea being something like this, but without the incorporated electronics and fake ears: https://3diosound.com/products/free-space-binaural-microphone

Right now my idea is a couple of these ( https://www.ikea.com/us/en/catalog/products/87077700/ ) with a dowel or some tubing between them.  The dowel/tubing could then be held in a Rycote INV-style shock mount.

So my first question is whether the cork of those hot pads would be sufficient to block sound and make an effective baffle?  If not, what could I do to make them better (or, what could fill that role better)?  Also, any ideas about attaching the baffles to the central connector, particularly in a way that they can be taken apart for easier storage in a bag?

Edit: Another idea for the baffles, which would be much smaller and thus easier to transport, is some wooden coasters.  Again, one on each end of the connecting dowel or tube of some sort.

I did something very similar to this for recording drum overheads with a pair of small omnis. I used two 45rpm singles with some camping pad foam glued to them threaded onto a piece of PVC. I tried a couple different ways but ended up using them spread about 5 inches apart with the mics around 1 inch from the barriers on the outside pointed slightly outward. I was looking to achieve a Jecklin disc type thing and it worked fairly well. I ended up using it on a lot of the percussion for the recording - there was a lot of percussion and once we got the drums to have that good stereo spread we found that miking the congas, bongos and other stuff the same way made the mix sit nice without too much panning.

I would suggest adding some foam or hairy fabric to the side of the disc to minimize reflections. If you use a single disc like a Jecklin it should be around 12" (people have done smaller with good results). If you use two discs and separate them they should get smaller the farther away they are.

The stereo separation happens largely in the high frequencies since the lower (longer) waveforms can get around the baffle.
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Offline rocksuitcase

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Re: Oddball microphone technique (OMT) - part 2
« Reply #114 on: July 16, 2018, 03:09:41 PM »
I've been thinking a bit about using a baffle with omnis in situations where really wide spacing isn't feasible.  One of the approaches I've been thinking about (and to be clear, I'm not claiming this is an original idea), is two small-ish circular baffles with some space between them and with the omnis mounted either flush or nearly flush with the surface of each baffle.  The general idea being something like this, but without the incorporated electronics and fake ears: https://3diosound.com/products/free-space-binaural-microphone

Right now my idea is a couple of these ( https://www.ikea.com/us/en/catalog/products/87077700/ ) with a dowel or some tubing between them.  The dowel/tubing could then be held in a Rycote INV-style shock mount.

So my first question is whether the cork of those hot pads would be sufficient to block sound and make an effective baffle?  If not, what could I do to make them better (or, what could fill that role better)?  Also, any ideas about attaching the baffles to the central connector, particularly in a way that they can be taken apart for easier storage in a bag?

Edit: Another idea for the baffles, which would be much smaller and thus easier to transport, is some wooden coasters.  Again, one on each end of the connecting dowel or tube of some sort.
I like the general idea. From a pure acoustics pov I would think the ikea 7" hot pads are as small as you would want to go. Don't forget all you are influencing at 7" or less (or any baffle small enough to hold in one hand) is high frequencies and going any smaller (less than 5" IMO) would not be worth it (i.e. your coaster idea)
Although, I've read maybe on TS where folks have used coasters on a tabletop as a sort of stereo separator.
« Last Edit: July 16, 2018, 04:15:57 PM by rocksuitcase »
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Offline heathen

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Re: Oddball microphone technique (OMT) - part 2
« Reply #115 on: July 16, 2018, 03:18:48 PM »
Do you think the cork would be fine on its own, or should I layer some other material with it?
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Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 2
« Reply #116 on: July 16, 2018, 05:31:54 PM »
We've talked about split-baffle ideas variations and in the past, both in the Oddball Mic Technique part 1 tread and in various Jecklin-disk threads.  I can't recall where specifically so you'd have to search them out.  The discussion in the OMT part 1 thread is probably somewhere close to the beginning, as I was messing around with Jecklin disks back in 2007 or so and strongly considered the idea of split small disks (I considered using clear CDR dummy discs) before going with the DIY spherical attachments instead.
 
I'll summarize a few issues which come to mind-

> Size of the baffle (and microphone distance from the baffle) determines the low frequency cut-off above which the baffle becomes effective.  Smaller = higher cut-off frequency.

> If mounting the mics right up against the baffle or flush-mounted in the baffle surface, it can be advantageous to use a hard, sonically-reflective baffle instead of a damped sonically-absorbent surface.  That creates a small boundary mount situation above the cutoff frequency.  That makes it unnecessary to try and evenly-damp the surface with respect to frequency, making the setup simpler and lighter-weight.  Mounting the mic on the baffle surface also maximizes the geometric "occlusion angle" - that is, how much the mic "sees" around the edge of the baffle, making a small baffle somewhat more geometrically effective above the cutoff frequency (the baffle "appears bigger" from the microphone's perspective, compared to spacing the mic away from the baffle, where it can "see further around the edges").

> If not mounting the mic directly to the baffle, use felt, foam, wool or a combination of materials to damp the reflection off the baffle.  To check effectiveness of the materials, hold the material against the baffle and place it close to your ear at an angle similar to cupping your hand to hear.  Play some music on the stereo and get up close to one of the tweeters.  Orient yourself so that the baffle is angled like a mirror reflecting the tweeter output into one ear.  Play with the baffle angle and listen for significant change in timbre of the reflected sound.  If it sounds brighter with the baffle reflecting the sound directly in, and less bright at other non-aligned angles, the damping material stands to be improved.

Raw cork will be quite reflective at these higher frequencies. It can work as a support disk, but think felt, wool blanket, or a couple layers of stuff like that glued to the cork disk.  Fur as used for wind protection isn't particularly good except maybe as a top cover layer, as the intent of wind protection fur is to not attenuate the high frequencies as much as practical.  You wan't the exact opposite for this- maximal attenuation within the frequency range in which the baffle is effective.

> Figure a way of adjusting the angle of the baffles on the bar, so you can play around with pointing them more forward rather than always facing directly to each side.
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Offline mjwin

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Re: Oddball microphone technique (OMT) - part 2
« Reply #117 on: July 16, 2018, 06:08:47 PM »
I've been thinking a bit about using a baffle with omnis in situations where really wide spacing isn't feasible.  One of the approaches I've been thinking about (and to be clear, I'm not claiming this is an original idea), is two small-ish circular baffles with some space between them and with the omnis mounted either flush or nearly flush with the surface of each baffle.
Some years back I made up a similar arrangement to that which you're suggesting.  To get close to head-spacing, I used 2 omni mics strapped together side to side but facing opposite directions, each with a right-angle xlr connector. Each mic protruded just far enough beyond its partner's rear XLR  connector to enable me to slip on a small baffle so that the mic diaphragm was flush with the surface.   In my case I wanted the whole thing to slide inside (an original) Rode blimp, so  the baffles were only 120mm diameter, and the holes offset in order for it all to align correctly.  I cut each baffle from rigid foam-core (art mount) board then glued a layer of softer foam to the outer surfaces.

The arrangement worked quite well for & wide ambiance & birdsong in the woods.  It also gave a much more realistic image with headphones than with speakers, which is what you tend to get with this kind of binaural arrangement.  The biggest problem for me was that the mics were too high-frequency directional left-right, so I couldn't actually point the array at anything!  I was using AT 3032 omni mics which are fairly typical for pencil omnis in being already quite directional above a couple of kHz. With the baffles in place I really did feel that there was a hole in the middle. 

It's interesting to experiment with baffle materials, though.  If you use a hard surface such as cork, you'll get more of a boundary effect at high frequencies, which will boost the top end up to 6dB or so. The larger the baffle/boundary, the lower will be the frequency at which this effect cuts in. Soft foam or felt will tend to act simply as a shield.  I think you'll need to make the discs out of something fairly rigid which can be slipped on/off at ease (wooden coasters sound ok),  then you can try different surface coatings, or even different materials each side so that you can swap around.  It doesn't seem to make much difference what, if anything, is between the baffles (as in that slightly wacky fake-ear contraption you linked to!)
 
I use the Rycote INV-7 shockmounts which are quite rigid, and one of these will easily hold your pair of mics in a fairly compact arrangement, then the baffles of choice can be slipped into place when you set up.  Thinking out aloud here, once you have the mics mounted you could also drop over a  single large (12") foam covered central baffle with a slit in it to get an approximation of a Jecklin disk. This will give a bit less shadowing to the front / rear, so might be better for capturing a performance of some sort.  But then, if you want a small rig, it might not be ideal.

There are a lot of subtle variations possible with this kind of arrangement and few hard & fast rules.  I always say:  if it sounds good, it is good:)

Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 2
« Reply #118 on: July 17, 2018, 09:58:01 AM »
Welcome to the thread mjwin.  Seems you'll be right at home here with these often DIY focused approaches.

The biggest problem for me was that the mics were too high-frequency directional left-right, so I couldn't actually point the array at anything!  I was using AT 3032 omni mics which are fairly typical for pencil omnis in being already quite directional above a couple of kHz. With the baffles in place I really did feel that there was a hole in the middle.
^
If using these split-baffled A-B omnis as part of a 3 or more channel OMT array, "hole-in-the-middle-ness" becomes a feature rather than a bug, and is filled by the forward-facing directional center microphone without excessive interference, but with just the right amount of overlap or with the omni pair.   And this is partly why I recommend figuring a way of adjusting the angle of the baffles as a way to experiment with facing them somewhat forward, say +/- 45 degrees rather than directly to the sides, which is likely to be more important if using the split-baffled omni pair on their own without a forward-facing mic or mic array in the center.

In my 6 channel setup, where I'm using sideways and forward-facing near-spaced supercards as the primary Left/Center/Right array for mid and high frequencies, I'd choose to angle the baffles backwards rather than forwards in many situations, to more strongly differentiate the diffuse ambience/audience reaction picked up by the baffled omnis from the front direct-arriving sound dominant in the L/C/R array.  The front direct-arriving and ambient diffuse-arriving lower frequencies which the omnis provide below the rolloff of the directional supercardioids are of a long enough wavelength that they will not be affected by the orientation of the baffles.  The only parameter which strongly affects the quality of the low frequency pickup is the actual spacing distance between the omnis, regardless of baffles or attachments.
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Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 2
« Reply #119 on: August 01, 2018, 01:16:43 PM »
Transfering a few posts to follow from another thread as they are OT there and really belong in this one instead.
 
These are near-spaced stereo setups which allow for varying pickup-pattern and in the second case the angle between microphones in combination with pickup-pattern, after the recording has been made.  Both require one to choose the desired spacing between microphones prior to recording, which is not adjustable afterwards.

They are indeed oddball in how they are set up, what they can do and the flexibility they can provide, yet are essentially standard near-spaced stereo pair arrangements otherwise.

Original thread is here- Unusual Schoeps MK8 (eBay Germany)
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<<

 

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