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Author Topic: Oddball microphone technique (OMT) - part 2  (Read 81552 times)

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Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 2
« Reply #120 on: August 01, 2018, 01:26:02 PM »
Near-spaced Straus-packet pair-

Here's a suggestion for a practical implementation for tapers who like using standard near-spaced stereo pair arrangements, which provides the capability to go back after the recording has been made and vary the pickup patterns of the microphones.

One needs two pairs of microphones with different pickup patterns and the ability to record all four channels. For maximum pattern flexibility use pair of omnis and a pair figure-8s.  Don't have omnis and eights?  This works for varying pattern seamlessly between whatever pairs of decently-matched microphones one has available - say between subcardioid and supercardioid, or between omni and supercardioid, providing the option of choosing any pattern in between the two afterward.   The setup will be cleaner and more easily managed if using all end-address microphones, or all side-address microphones.

Arrange the mics in two pairs such that in each pair the two different-pattern microphones form a coincident pair, with one directly above the other and both facing the same direction.   Do the same on both sides of your favorite near-spaced stereo pair arrangement.  Use standard over/under-style Mid/Side mounts and windscreens (with each omni/supercard pair in this example facing the same direction).  Record all four channels.  Afterwards, cross-fade between the omnis and supercards to derive whatever pattern you wish between the two. 

Can use a standard Mid/Side decoder to do the cross fading if you like, by feeding the omni into the Mid input and supercard into the Side input, and using only the Left channel output.  100% Mid = omni, 100% Side = supercard, 50/50 ratio = subcardioid, choose any pattern you wish in between.  Do that for both sides of the near-spaced stereo pair. 

Otherwise just mix the two to find what combination works best, and don't worry about what patterns you actually end up with

 

If needing even more control, one can use this method to choose slightly different patterns for Left and Right, and/or apply differential EQ to vary pickup pattern by frequency and do so independently for each side.
« Last Edit: August 01, 2018, 05:22:50 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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 2
« Reply #121 on: August 01, 2018, 01:31:08 PM »
Two Mid/Side pairs as near-spaced stereo array providing variable pattern/microphone-angle-

This is a very interesting setup possibility for a near-spaced stereo pair.  The more I think about it, the more I like it.  Near-spacing distance between microphones remains constant, yet this allows one to vary both pickup-pattern and microphone angle.  Choice of pattern and angle is linked, just as with standard Mid/Side.  First thought and most straightforward would be to set this up with both Mid/Side pairs parallel to each other and pointing directly forward.  However, pointing the two Mid/Side pairs such that they face directly to either side instead of forward offers a far more useful range of pattern/angle combinations. In which case, adjustment of the Mid/Side ratios allows one to vary pattern/angle between forward-facing parallel figure-8's (Sometimes described as a Faulkner phased array) through cardioids with a 180 degree angle between them.  At Mid/Side ratios in between those extremes one will derive supercardioids with an angle somewhat wider than 90 degrees and hypercardioids at a somewhat narrower angle.  Pattern and angle can be varied seamlessly across this spectrum after the recording has been made, with the decision of what sounds best made by ear.


Setup for two near-spaced M/S pairs-

Use two Mid/Side pairs with cardioid Mids.  Space the two pairs 17cm apart (or 20, 25, 30cm or whatever near-spacing you want), and angle them such that the Cardioid Mids are facing directly to the sides (180 degrees away from each other). Both Side microphones should have their positive polarity lobe facing forward, so flip the Side figure-8 of the Left pair so that it's positive polarity lobe is facing forward instead of rearward. 

Record both raw M/S stereo pairs (4 channels total).  Let's call the Left-side M/S pair- pair 1, and the Right M/S pair- pair 2.
After recording, you run both raw Mid/Side pairs through Mid/SIde to Left/Right decoders.  The Left output of Pair 1 is routed to Stereo Left.  The Left output of Pair 2 is routed to Stereo Right. Set the ratio to determine the pattern and angle (both remaining linked, as it always does with standard Mid/Side) from forward-facing figure-8 through sideways facing cardioid.  Typically one would use the same ratio for both Mid/Side pairs, but one could use different ratios on each side to choose different patterns and angles for Left versus Right.

Cool multichannel surround / ambience channels option-

The Right channel outputs from both Mid/Side decoders provide rear-facing virtual microphones with a pattern and angle that mirrors the forward-facing microphones on either side.  If you understand how to dial in a different Mid/Side ratio for Left versus Right in a typical stereo Mid/Side setup, you'll see how you are able to choose a different combination of pattern and angle for the rear-facing ambience channels.


A few thoughts-

While going through this, after realizing that it makes more sense to point the Mid/Side pairs sideways instead of forward and makign the drawings, I realized that there is nothing new under the sun.  Kudos to Jerry Bruck and Schoepes for basically pioneering this approach already with their KFM 360. This is basically the KFM 360 arrangement except substituting cardioids for the flush-mounted sphere baffled omnis.

Over a decade back, I schemed about of ways of emulating the KFM360 as a lower-cost, headworn HTRF setup.  I ended up going with an alternate 4-channel setup which did not use Mid/Side pairs. Still these ideas have been been in the back of my mind since then, and this seems a setup that seems far more practical actual real taper use.
« Last Edit: August 01, 2018, 03:07:24 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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline EmRR

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Re: Oddball microphone technique (OMT) - part 2
« Reply #122 on: August 01, 2018, 05:02:29 PM »
I applaud the use of MS with spaced pairs.   Seems like best of both worlds. 

I've been playing a bit with DMS to change the M pattern.  I suppose you could do a pseudo-spaced variant with the use of delays on both the DM signals and duplicated S signals.  Clearly not the same, but may have possibilities for front to back depth perception, and once enough delay is introduced polarity flips on the duplicated S might get useful.  You could make a huge mess too.  So far I've only tried delaying one of the M elements to good effect. 

Down that tangent, a good head stretching exercise, it was pointed out that a mic like the Sennheiser MKH800 Twin or Lewitt LCT-640-TS can be used as a stereo mic, and the pattern is really the 'same-as' MS with an omni M.  To check it out, I duplicated the source, converted one to omni and the other to figure 8, then ran those through MS processing.  I really couldn't detect an obvious difference comparing direct result with matrixed result.  Anyway, a nice head game to make you think about possibilities and realities.  I expect doing 'proper' MS with omni M would have a very different sonic tilt due to the differences in proper pressure omni versus constructed pressure gradient omni, along with the high frequency directivity differences between the two approaches (90ยบ difference in this example). 


Carry on....
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Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 2
« Reply #123 on: August 01, 2018, 06:39:17 PM »
Yeah, Mid/Side stuff is fun to think through.

The next logical step with the near-spaced Mid/Side pair setup described above would be to replace the two standard Mid/Side pairs with Double-Mid/Side setups.  One could then adjust the pickup pattern and microphone angle independently. And because of that, one could set it up with both Double-Mid/Side setups pointing directly forward.  Cool thing is that would only require 6 recording channels in total to make that work.
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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 2
« Reply #124 on: August 01, 2018, 06:39:52 PM »
I really couldn't detect an obvious difference comparing direct result with matrixed result.

I've noticed playing around with Ambisonics (basically the same as Double-M/S in the horizontal plane) that it can be very difficult to discern changes of pattern when listened to in isolation (mono), especially with recordings made out in the diffuse field at a significant distance from the source, except for listening for low-frequency response differences (omni providing the most low bass, figure-8 the least).  It's really only when two or more channels interact with each other (electronically or in air) that the differences come to the perceptual fore.  For instance, except for the low bass response, an omni and a figure-8, both placed out in a diffuse environment sound about the same, while a pair of coincident omnis verses a pair of coincident crossed fig-8's sound obviously and completely different when listened to in stereo.

Yesterday when thinking about and writing up my posts on PolarFlex in the other thread, I found a sample player embedded at the bottom of the Schoeps PolarFlex plugin web page.  It allows one to listen to two different recordings using a stereo pair of PolarFlex'd microphones.  One is a main microphone pair (diffuse field) and the other a pair of stereo piano spots (much closer).  For each source, one can choose between listening to the stereo omnis in isolation, the stereo figure-8s in isolation, and between two different PolarFlex combinations of those mics.  The two combinations are polar opposites (pun) in terms of their polar response's varying by frequency. One is omni directional at low frequencies morphing to bi-directional at high-frequencies, and the other more or less the inverse.

What is interesting is using the sample player to listen for what I describe above.  Start by putting only one headphone ear cup on (or otherwise selecting only the Left or Right channel to monitor).  With the more distantly mic'd main-pair sample, switching between the solo-pre omni and solo-pre fig-8 sounds more-or-less identical.  Yet when listened to in stereo the difference is easily discernible.   Likewise with the two PolarFlex settings- listening the a single channel they sound more or less the same except for a somewhat larger frequency balance difference than the omni and fig-8 solo'd.  Yet when listened to in stereo the difference is immediately obvious.

With the stereo piano spots recording the differences between the solo-pre omni and fig-8 are greater due to the closer "free-field" mic positioning, yet the same basic trend holds- the differences are far more discernable in stereo than as a mono feed of either channel.

Link to the page- https://schoeps.de/en/products/spezialmikrofone/polarflex/polarflex-plug-in.html
Sample player in at the very bottom on the right side of the page.


[Edit]- I also notice the same with the my OMT setups. On more distant diffuse-field recordings, the individual channels often sound almost identical to each other when listened to in isolation, other than the basic frequency response differences of the microphones themselves.  It's only upon combination that various spatial qualities and properties emerge.  That aspect is rather analogous to holography in this way (holophony?).  Where as for small room and closer-perspective recordings, I'm more often able to easily hear the differences between channels in isolation.
« Last Edit: August 01, 2018, 06:51:33 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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline rigpimp

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Re: Oddball microphone technique (OMT) - part 2
« Reply #125 on: August 02, 2018, 11:32:02 AM »
OK, I'm on board the oddball train.  I've run fixed ORTF and MS for a while now and I really enjoy MS for being able to dial it in different directions in post.  I now want to goof around with the Schoeps Polarflex plugin.  While I do not have MK2's I do have matched pair of MK5's and with a matched pair of MK8's so it seems silly not to try something weird. 

With that said I have reached out to Scott at SRS so see if he can make the mounts.  I have sent him gutbucket's sketch and the Schoeps brochure showing the Polarflex mount.  I'll report back with any progress as it has been made.
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Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 2
« Reply #126 on: August 02, 2018, 11:55:21 AM »
Cool. Will be interested to hear how it works out.
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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline noahbickart

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Re: Oddball microphone technique (OMT) - part 2
« Reply #127 on: August 02, 2018, 01:02:21 PM »
This is all very intriguing. With 2x MK4v + mk8 I can do double m/s and still have from on the mixpre6 for a
Pair of spaced mk2xs omnis. Hmmmm.
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Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 2
« Reply #128 on: August 02, 2018, 03:29:43 PM »
Had you in the back of my mind thinking about this Noah, as I know you have both the mics and the predilection to pull it off.

You probably want to keep your wide-cardioid MK22s in your standard reference setup, but it may be useful to try them as Mids in place of the cardioid MK4Vs.  Doing so would shift the virtual cardioid pattern of the Mid/Side adjustment range somewhat forward rather than pointing directly to either side, and open up the other virtual patterns slightly for the same virtual angle.  It's likely that using the MK22s as Mids you'll just want a bit more spacing between pairs, same as with standard near-spaced setups using various pickup patterns.
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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline kuba e

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Re: Oddball microphone technique (OMT) - part 2
« Reply #129 on: August 02, 2018, 04:26:32 PM »
Thanks a lot for interesting posts, I will read it more times. And thanks for nice sketch which makes it clear.

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Re: Oddball microphone technique (OMT) - part 2
« Reply #130 on: August 02, 2018, 06:01:55 PM »
To add: kindms and I have done single M/S inside of split omnis (100cm). It can be very yummy and also provides you with a solo 2 channel mix if you just want a "backup" in case you don't prefer the spaced omni contribution. I wholeheartedly endorse this double MS configuration. We don't have the proper combination of mics to do this however. lol
We have the 414's and any number of cardiods though to do a rough version.

rigpimp and noah I really think that each of your combos of Schoeps would result in a great recording.
Thanks GB
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Offline EmRR

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Re: Oddball microphone technique (OMT) - part 2
« Reply #131 on: August 02, 2018, 10:49:48 PM »
it can be very difficult to discern changes of pattern when listened to in isolation (mono), especially with recordings made out in the diffuse field at a significant distance from the source, except for listening for low-frequency response differences (omni providing the most low bass, figure-8 the least).  It's really only when two or more channels interact with each other (electronically or in air) that the differences come to the perceptual fore.

Very true. 

I neglected to say the sample I experimented with was a stereo drum kit recording at about 6 feet out, so very definite spread in the free field. 
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Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 2
« Reply #132 on: August 03, 2018, 11:45:48 AM »
I've thought about incorporating these kinds of sideways-facing Mid/Side pair arrangements in multichannel OMT setups.  Several are mentioned in the latter pages of the OMT illustrated PDF booklet I uploaded near the end of the OMT part 1 thread last year.  What is different in the recent posts above is simply applying the same concept to more typical near-spaced stereo pair setups.

Attached is a PDF showing a few OMT variants using sideways-facing Mid/Side pairs-
The first is a 6-channel setup consisting of 3 Mid/Side pairs:  It starts with a standard Mid/Side forward-facing pair in the center between two wide spaced omnis - the setup rocksuitcase just posted about above.  It takes that and adds front/back facing fig-8s coincident with the wide-spaced omnis, turning them into Mid/Side pairs with control over front/back directivity.  That provides full-range pattern control (omni>subcard>cardioid>supercardioid>figure-8) over the wide-spaced omnis with the ability to choose if those virtual patterns face forward or backward.

The second two are 8-channel OMT setups which I hope to experiment with next, both variations on the 6-channel arrangement I'm currently using, with the near-spaced front/back OCT setup (Double-OCT?) in the center rather than a Mid/Side pair in the center.   

In the first of these I plan to place figure-8s with the omnis to form front/back Mid/Side pairs just like the 6-channel version above, but using the OCT arrangement in the center.  I suspect this will be advantageous in good acoustics and outdoors, by providing the ability to reduce the sensitivity of the wide omnis to direct sound arriving from the front, providing the ability to use more ambience, audience and room-sound from the wide omnis without getting excessive direct sound through those channels.

The second 8-channel variation places the two figure-8s coincident with the sideways facing Left/Right OCT supercardioids instead of the omnis, providing the ability to dial in forward angle for those channels which may prove helpful in smaller rooms and difficult acoustics.   This is very similar to the near-spaced Mid/Side pairs setup outlined above, except with the addition of the front/rear-facing center mics and wide omnis.

[Edited to update PDF with 3rd array, and update description above]
« Last Edit: August 03, 2018, 12:13:58 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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline heathen

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Re: Oddball microphone technique (OMT) - part 2
« Reply #133 on: August 03, 2018, 12:18:59 PM »
Sorry to veer off course a bit here, but I've been thinking about four channel setups like a pair of spread omnis with a pair of directional mics in the middle.  What I'm wondering about is the relationship between the SRA of each pair to the other.  So, using that Sengpiel Audio visualizer tool, if I have a pair of omnis 60 cm apart then that gives me a SRA of 118.1 degrees.  Assuming that's the right SRA for the specific location/circumstances, should the directional pair's SRA ideally be the same as that of the omni pair (assuming something like mid/side that can be adjusted in post isn't being used)?  If the SRAs are significantly different, won't the blend of mics result in a weird stereo image?

(I should add that the end goal here is stereo playback.  I imagine that surround/multi-channel playback as the end goal would have a different impact.)
« Last Edit: August 03, 2018, 12:44:26 PM by heathen »
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Offline rocksuitcase

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Re: Oddball microphone technique (OMT) - part 2
« Reply #134 on: August 03, 2018, 12:23:59 PM »


[Edited to update PDF with 3rd array, and update description above]
I grabbed it and added to the others. THANKS so much Lee!
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