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Author Topic: Oddball microphone techniques - part 1  (Read 165794 times)

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Offline Gutbucket

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Decorellation of Audio Signals and Its Impact on Spatial Imagery
« Reply #330 on: November 09, 2017, 02:38:37 PM »
Before we moved on to other stuff, I'd revived this thread with a discussion of decorrelation, starting with this post about 4 pages back - https://taperssection.com/index.php?topic=96009.msg2244172#msg2244172

Here is an excellent paper on the topic I recommend to anyone interested in digging deeper into the effects of decorrelation on stereo signals - The Decorrelation of Audio Signals and Its Impact on Spatial Imagery - Gary Kendall (1995) - http://www.garykendall.net/papers/Decorrelation1995.pdf
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 techniques
« Reply #331 on: November 13, 2017, 05:01:53 AM »
I tried the oddball technique for the first time. It's great technique, it gives us plenty of options to influence the final sound of the recording. The ability to change the ratio of direct sound and ambience, and add depth is perfect.I'm sure more people will start using this configuration. I'm not good at post processing, but I see this mics configuration is big help to achieve great results. Last weekend I made a trip to Munich in Germany for the Gov't Mule concert. The music was great and there were six tapers too. It was great to meet them. They were interested in this technique too. I sended them a link to this thread.

Unfortunately I came late to the club, the lights were off, no photo went well. At least I took the picture of the club at the end of the concert when they turned on the lights. And I took the picture of the microphone stand at home later. We were setup at sbd about 50 feet from the podium. The mics configuration was:
the forward & rear cards: nak300, spacing 13 inch
spaced omni: ca11, spacing 4 feet.
https://drive.google.com/drive/folders/1MKdygDhUAO1tSdNMz6pkwXxuCXRUsrBO?usp=sharing

Post processing is very difficult for me. I'm not sure at all. It was difficult to mix the recording, but I believe it will be better and easier next time. What surprised me very much was when I mixed the front and rear microphones in M/S. The result is very good. M/S is dominant in the final mix, omni are only slightly added there. When I added more omni, it did not sound good. Maybe I spaced them too much. Could I add more omni in the mix if they are less spaced?

I'm sending a sample. In the end, I did not choose it well, omni stereo is not well balanced there. (In the first set it was better balanced, maybe the stand was moved little. I balanced the second set omni by the gain and short delay of the left channel when mixing the final mix.) But I hope it would be enough to illustrate. There is sample of Hans's recording too. He had the stand right next to me with MBHO cards, din. It's for comparsion how it sounds single pair.
https://drive.google.com/drive/folders/1MLNWhfUh9eTgUgE22V2rcJH6QsG_Zpch?usp=sharing

Gutbucket, thank you for your explanations and for reference to the theory. I love to read it. It will take me a while, but then I will write back. I was thinking about the little thing relating to the theory when I was processing M/S. When there is a large part of S and M is weak, then much of the signal in the right and left channels is in the opposite phase. Is the partial opposite phase in the left and right signal what makes special sound in M/S (maybe blumlein too)?

Medeski and those guys should have no problems with recording AUD as long as the room allows it you should be AOK!
I'm just a bit jealous as I haven't seen Medeski in a couple of years and always enjoy his side projects (sometimes more than MMW)
I also like very much their side projects. It would be difficult to make decisions when I could choose. But I would probably go to Medeski and friends, Wicked Knee or Wood Brothers than MMW. Perhaps this is because their side projects can be seen in small clubs and in a very relaxed atmosphere.
« Last Edit: November 13, 2017, 06:28:16 AM by kuba e »

Offline Gutbucket

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Re: Oddball microphone techniques
« Reply #332 on: November 13, 2017, 10:54:37 AM »
Glad you got a chance to try these techniques and are enjoying doing so.  And thanks for the report, photos and samples.

Post processing is very difficult for me. I'm not sure at all. It was difficult to mix the recording, but I believe it will be better and easier next time. What surprised me very much was when I mixed the front and rear microphones in M/S. The result is very good. M/S is dominant in the final mix, omni are only slightly added there. When I added more omni, it did not sound good. Maybe I spaced them too much. Could I add more omni in the mix if they are less spaced?

I've downloaded your samples and will play with them myself when I get the chance. [question- in the front/back pair recording which is in the left and which is in the left channel?] I did a quick listen to each source on this computer and I don't think less omni spacing would make for an improvement or allow you to use more of them in the mix.  Listening to the omni pair alone I don't hear any problem with excessive spacing, but do want to make some significant EQ corrections.  I suspect that's mostly what you are hearing more than an effect from the microphone spacing. 

I typically start mixing that way with the omnis- EQ and level balance the omni pair alone to best effect, then add the center pair.  But you can also do it the other way around if your recording is stronger that way- make the Front/Back, Mid/Side pair primary and bring in the omnis in support of that.  The EQ on the omnis might then be somewhat different, possibly with less mid emphasis (getting more of that from the M/S pair), rather than boosted lows and mids with a carefully cut "mud and boom" region in-between, typically centered somewhere around 300Hz. Omnis can be tricky and commonly need some EQ manipulation to work around the room resonances in that bass region when indoors in a strongly PA amplified room. The top end EQ often depends more on the characteristic of mics and how smooth they sound up there.  I'd have to play around with your samples before commenting there and expect your omnis may want only a bottom and mid emphasis with some top end reduction and the aforementioned cut around 300Hz.

Quote
I was thinking about the little thing relating to the theory when I was processing M/S. When there is a large part of S and M is weak, then much of the signal in the right and left channels is in the opposite phase. Is the partial opposite phase in the left and right signal what makes special sound in M/S (maybe blumlein too)?

Yes, there are definite parallels there.  One of the interesting things to me is how sufficiently randomized phase of the diffuse room sound (via sufficient mic spacing) sounds similar to having inverted polarity in each channel (via Blumlein or Mid/Side with sufficient Side content), even though one relies on spacing and the other is coincident.

Thanks for the post!
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 techniques
« Reply #333 on: November 13, 2017, 12:10:49 PM »
Embedding kuba e's mic setup photos in the thread-


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 techniques
« Reply #334 on: November 13, 2017, 12:11:41 PM »
Front/back pair detail-

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 rocksuitcase

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Re: Oddball microphone techniques
« Reply #335 on: November 13, 2017, 12:42:00 PM »
kuba e: my input regarding mixdown:
Mostly follows Gut's input. I usually load all four channels into the Processing software (I use Audacity). then I focus on the stereo pairs. With the Omni pair, recorded in an indoor room, typically do a lot of listening (speakers, headphones, car speakers) then decide on a EQ scheme. Often, the boominess inherent with the Omni needs some low frequency reduction. that 300Hz region typically needs reduction, I tend to start the reduction at 400Hz then down all the way to 20 Hz. The main idea here is to make the Omni pair sound good with less low frequency boominess. I typically don't worry about anything above 3KHz with the Omni pair as those frequencies get emphasized with the middle card pair.
I then change the card channels to two channel mono labeling the front and rear channels properly (I am NOT dealing with MS option here). I then take the rear mic and lower it by 6-10 dB as compared to the front facing mic. Then I start blending the front and rear into the mix, setting the balance between omni sides and front/rear using the solo or mute buttons. You then have a 4 channel mix with the omni pair EQ'd and can either apply EQ to the front/rear channels as you see fit, OR mix down to two channels then EQ the resulting mix.
I don't do the MS mixing I leave that explanation to Gutbucket.
« Last Edit: November 13, 2017, 03:32:36 PM by rocksuitcase »
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Offline morst

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Re: Oddball microphone techniques
« Reply #336 on: November 13, 2017, 02:11:37 PM »
The term "MID" is used for two different things in this conversation - the M in M/S and also Midrange. Please be sure to specify, if you don't mind, these new techniques are a bit confusing to read about anyhow!

If I get into this, I'll want more than 4 channels soon enough... may have to fire up the laptop and MOTU 828 again!?

.....I typically start mixing that way with the omnis- EQ and level balance the omni pair alone to best effect, then add the center pair.  But you can also do it the other way around if your recording is stronger that way- make the Front/Back, Mid/Side pair primary and bring in the omnis in support of that.  The EQ on the omnis might then be somewhat different, possibly with less mid emphasis (getting more of that from the M/S pair), rather than boosted lows and mids with a carefully cut "mud and boom" region in-between, typically centered somewhere around 300Hz. .....
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Offline kuba e

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Re: Oddball microphone techniques
« Reply #337 on: November 13, 2017, 03:09:07 PM »
Thank you for help with eq and mix, it's very useful for me. Post processing and eq are very demanding, and there is also a need for sound sensitivity. The recording sounds bad in the speakers but I could not fix it. At least it sounds good in the headphones. I have to learn step by step. I'll try another try.

[question- in the front/back pair recording which is in the left and which is in the left channel?]
I think front mic is in the left channel. I'm not sure about one hundred percent. When I set my microphones, I did not mark it. I'll mark it next time.
« Last Edit: November 13, 2017, 03:11:22 PM by kuba e »

Offline Gutbucket

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Re: Oddball microphone techniques
« Reply #338 on: November 13, 2017, 03:36:28 PM »
The term "MID" is used for two different things in this conversation - the M in M/S and also Midrange. Please be sure to specify, if you don't mind, these new techniques are a bit confusing to read about anyhow!

Yes, good point! I'd try to say midrange when referring to frequency.

.....I typically start mixing that way with the omnis- EQ and level balance the omni pair alone to best effect, then add the center pair.  But you can also do it the other way around if your recording is stronger that way- make the Front/Back, Mid/Side pair primary and bring in the omnis in support of that.  The EQ on the omnis might then be somewhat different, possibly with less midrange emphasis (getting more of that from the M/S pair), rather than boosted lows and mids with a carefully cut "mud and boom" region in-between, typically centered somewhere around 300Hz. ..... [edited]

And agreed with rocksuitcase, except that when dialing in that upper bass/lower midrange cut (which is often significant indoors and can range anywhere from 120 to 500Hz), I almost always carefully boost the lows below that range to restore the deep bass which is a big part of the realism I feel the omnis uniquely provide.  I may cut the very lowest frequencies if its only non-musical noise, but I'm probably boosting between there and the upper bass/lower midrange reduction, else the overall solid bass which the omnis are supposed to contribute gets anemic.   With a cut on either side, that range gets pulled down along with its neighboring regions and needs a boost to bring it back to where it should be.

Of all the raw tracks you posted, that the Mid/Side mixed front/back pair sounds best to me prior to any other manipulation, so using that as your starting point here seems apt. I often bump the 2-3kHz area of my omnis for clarity and that seems relatively common for most omnis.  Its the frequency range above 3kHz where different mics seem to behave quite differently and its harder to make general statements about what to expect there.  Quite frequently I'm reducing the omni content in that region if the center mics are taking care of it nicely, yet bring the omni level back up in the high treble around 14kHz or so to get some nice open diffuse ambient air.  But that really depends on the mics and situation.  Might make sense to smoothly reduce all the highs from the omnis above 3kHz if they are bright sounding to begin with or if that content conflicts with the same frequency range provided by the center pair.

Quote
If I get into this, I'll want more than 4 channels soon enough... may have to fire up the laptop and MOTU 828 again!?

One of the keys to not going crazy with complications is keeping things manageable.  If you can do that with a laptop and interface, great.  Everyone needs to find their own comfort level, and even 4 channels is more than many tapers want to have to manage.  Nothing wrong with that.  The only way I can do 6, 8 or more channels is to set most of it up beforehand so I can pretty much just roll at the event.  For the last two open-setup recordings I posted about above, the first using the 4 mics took me about 4 times as long to arrange and setup at the show, and also break-down afterwards, compared to the 6-channel pre-wired miniature mic setup I ran a couple days later.  For that one I just popped up the stand and pointed the mics, fired up the recorder, adjusted levels and rolled.  Quick and easy on the recording side of things.  More to manage on the back side once recorded, but that's the nature of these setups.

Quote
I think front mic is in the left channel. I'm not sure about one hundred percent. When I set my microphones, I did not mark it. I'll mark it next time.
 
Thanks.  I may be able to tell by listening.  You'd think it would be obvious, but it can be amazing how similar the different channels can sound in isolation. It's the interaction between them where identity arises.  And yes, always keeping the forward facing mic in the left channel and rear-facing in the right is good practice, and it makes Mid/Side decoding straight-forward.

I've found that as the mic count increases, its extremely helpful to do a mic check either just before or just after the performance, all setup in place, snapping fingers or speaking directly into each mic to ID which channel in a short separate recorded file-set.  More often than I would have expected or care to admit, I've found accidental left/right channel pair swaps or even messier channel mis-routings I did not intend and might not have noticed otherwise.  That's another complication pre-wiring everything helps me avoid, yet I still like to do the check.  I actually keep a dog-clicker in my bag which helps with those mic IDs in loud environments.
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 techniques
« Reply #339 on: December 03, 2017, 11:12:12 AM »
I'm not sure if this counts as an oddball technique, but I tried a Straus packet setup over the weekend.  I had AT4031s set up PAS, then I took Countryman B3s and taped them to the ATs so each B3 was coincident with each AT.  Unfortunately I didn't take  a photo but hopefully that makes sense.

So far I've only processed the opening band, but for that one I ran the B3 source through a LPF at about 200 hz, then mixed that with the AT source.  I had the B3 source at -10 dB in Audacity.  Here's the opener: https://archive.org/details/Genetics2017-12-01.AT4031.B3.flac16/Genetics2017-12-01.AT4031.B3.t03.flac

The main act had their own sound guy, and their mix was a bit better, so I'm not sure if I'll do things exactly the same for the headliner.  I had it set up the same at the show though.
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Offline rocksuitcase

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Re: Oddball microphone techniques
« Reply #340 on: December 04, 2017, 10:14:29 AM »
Another "classic OMT" I finally just upped to LMA: http://taperssection.com/index.php?topic=184505.0
                                                                 24 bit    https://archive.org/details/adamezra2017-08-16.akgck22ck1-24           

recording Info:
location: 40 feet from stage 8 feet up
ch1|2 AKG ck22|460 omnis spread 100cm
ch3|4 AKG ck1|460 cardiod naiant active fwd 0'|rear 180'
Tascam DR680|SD

Three pics- two of the show set-up. The third is when the band came out into the audience, directly below the rig and I twisted the stand around to center on them.
« Last Edit: December 04, 2017, 10:59:22 AM by rocksuitcase »
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Offline Gutbucket

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Re: Oddball microphone techniques
« Reply #341 on: December 04, 2017, 10:35:48 AM »
^ Looks like a cool venue right on the edge of the lake.

I'm not sure if this counts as an oddball technique, but I tried a Straus packet setup over the weekend.

I tried that a few times with the DPA omnis gaffer-taped onto my Gefell cards or supercards, but never really got it to work very well.  Always worked much better for me to not try and place them coincident but to space the omnis further apart than the directional mics.  Fun stuff to play around with regardless.
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 techniques
« Reply #342 on: December 04, 2017, 11:12:31 AM »
I mostly just did it as an experiment.  At least for the headliner, I didn't feel like the AT4031s needed any "help" so I didn't mix any of the omnis in.  Listening back, the omnis may not have been necessary for the opener either.

Re: further spacing... This was just an experiment, and it was pretty easy to set them up like this rather than rig up another thing to accommodate the greater spacing of the omnis.  Outdoors I'd definitely want to space them further in the future.  Indoors, I just don't know that I will find it necessary to run the omnis at all.  Maybe if I come across a venue that sounds good enough that I want more room sound than I'm already getting...but indoor venues that nice are not where I typically find myself taping.
Mics: AT4050ST | AT4031 | AT853 (C/SC) | Line Audio CM3 | Sennheiser e614 | Sennheiser MKE2 | DPA 4061 Pre: CA9200 Decks: Zoom F8 | Roland R-05

Offline Gutbucket

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Re: Oddball microphone techniques
« Reply #343 on: December 04, 2017, 11:28:20 AM »
When I tried it, it was inside and sort of a last minute thing each time, and I wasn't setup to space the omnis further anyway so it was easy to just tape them to the near-spaced cards/supers.  But it just made for a boomy mess for me and was better without the omnis.  I hesitated after that to use wider-spaced omnis inside for the same reason, but they seem to work much better for me.
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 techniques
« Reply #344 on: December 04, 2017, 12:14:42 PM »
Perusing an old thread, I came across a comment that seems appropriate for this thread:

Quote
The not at all simple alternate answer which potentially could help adjust for being off-center has to do with adjusting the microphone configuration in combination with rotating the stand.  It's probably far more trouble than it's worth, would be hard to do precisely in the field, and is not something most tapers would want to try, but is interesting to me technically.  I won't go into it here in too much depth, but it has to do with adjusting the angle of each microphone so they are no longer in a symmetrical arrangement with the center axis of the microphone array.  Essentially, one microphone is moved forwardof the other, and that accomplishes something similar to the delay thing I described previously, "at the microphone array" itself.

That's based on the work of Michael Williams which explores the inter-relationship between pickup pattern, angle, spacing and position of a pair of microphones.  It's how he goes about "linking" multiple microphone pairs together to form multichannel surround recording arrays which are capable of seamless playback imaging between across each microphone/speaker pair sector, without gaps or overlaps.  His papers on Multi-Microphone Array Design (MMAD) explain this in depth, but are more technical than most tapers here will care to get into.

This was in the context of a question about what to do when setting up off-center from the sound source.  The bolded part has me most intrigued.  I find it really distracting when I'm listening and the whole sound is noticeably off-center.  Obviously sometimes we can't set up at the center line for whatever reason.  I've found that just raising the level of the more "distant" channel is often unsatisfactory...maybe because the volume level doesn't make up for time of arrival differences in the channels?  So, I'm curious about the practical application of the idea hinted at in the quote above.  If we're talking about a near-coincident stereo pair, would putting one of the mics closer to the sound source help mitigate being off-center more than simply raising the gain of one channel?  I'm guessing that the mic on the more distant side would need to be moved closer.  How much of a change in location are we talking about, though?  If we think of it in terms of just a simple PAS config, would each of the mics be pointed at the stacks after adjusting the forward location of the one mic?  Or before making that adjustment?
Mics: AT4050ST | AT4031 | AT853 (C/SC) | Line Audio CM3 | Sennheiser e614 | Sennheiser MKE2 | DPA 4061 Pre: CA9200 Decks: Zoom F8 | Roland R-05

 

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