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Stereo Recording a circular ensemble Condenser Microphones
Old 25th December 2018
  #1
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rojaros's Avatar
Stereo Recording a circular ensemble

I wonder what would be the best microphone configuration to catch a the room sound of a small ensemble that is playing in a circle?

I thought of something like the 4-channel ORTF surround like here further down: ORTF-3D.

But then, how would I mix that to stereo?

Or any other suggestions? Double NOS? or three cardioids spread over 120° each?

Thanks for advice!

And still merry Christmas
Old 25th December 2018
  #2
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Stradivariusz's Avatar
If you know how to do it it's often done by just a single pair of omni mics. Sometimes with more omni mics, placed close and nicely mixed together. I didn't see there any main pair than. See some engineers from Outhere (Europe) has done this like Hugues Deschaux (Alpha recordings) for example.

In the first example you spend more time to make a good balance, in a second example you spend more time mixing after the recording.
Old 25th December 2018
  #3
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Manuel Mohino is another example.
Old 26th December 2018
  #4
If they're in a circle around the mics, I just use Blumlein. Whether I use ribbons or LDCs would depend on the music.
Old 26th December 2018
  #5
Hi TM! -- Blumlein can cause some problems in this scenario. Sources from the front are in-phase with both capsules (good), but as the sources move past 90*, they will reach one capsule in-phase and the other capsule out-of-phase (bad). In a nutshell, one half of your sources will have extreme phase cancellation.

You can hear this on some "one mic only" showcase videos.
Old 26th December 2018
  #6
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I probably prefer the John eargle method using a pair of omnis in the center, slightly above the players. It avoids phase and imaging difficulties and gives good low freq response.
Old 26th December 2018
  #7
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Simple if you have enough mics and mounting bars to cover all the sensible options mentioned above....prepare the arrays ahead of the rehearsal time, and ideally on 2 or 3 stands.

Time and speed of the essence here.....you want to avoid changeover time delays as much as possible...replugging the mics should be the only onsite wrangling you'll want to do, nothing else !

Test at least 3 arrays during the rehearsal session (assumption ...there will be a rehearsal in the actual venue, yes ? There will be a day or a few hours at least within which to audition the test and determine which you prefer best ...yes ?)

I'd recommend spaced Omni, back to back ORTF and 120 NOS x3..... and more if you wish, and have enough mics to manage it ?

10-15 mins per array is all you require...run and gun

What....you say they won't even give you rehearsal/experimentation time a few days before the concert/session ? "We can't afford the hire of the room for another 2 hours" ?

Scum....
Old 26th December 2018
  #8
Quote:
Originally Posted by NorseHorse View Post
Hi TM! -- Blumlein can cause some problems in this scenario. Sources from the front are in-phase with both capsules (good), but as the sources move past 90*, they will reach one capsule in-phase and the other capsule out-of-phase (bad). In a nutshell, one half of your sources will have extreme phase cancellation.

You can hear this on some "one mic only" showcase videos.
I need to go look at notes - we recorded quite a bit of jazz horn sections this way.
Old 26th December 2018
  #9
Quote:
Originally Posted by TMetzinger View Post
I need to go look at notes - we recorded quite a bit of jazz horn sections this way.

And the answer was that they were in two arcs, not a full circle.
Old 26th December 2018
  #10
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Simmosonic's Avatar
 

For that situation I’ve used an MS pair with an omni M capsule. Assuming you have matched the sensitivity and gain of the mics, at 1:1 MS ratio it decodes to two back-to-back cardioids, coincident, with none of the phase issues associated with spaced microphones. With a little bit of direction you can sort out the circular balance quite well. And, FWIW, decodes to a single omni in mono.

I’m using it in this pic with a pair of Rode NT2000s, directing the ensemble a bit to get the right balance...
Attached Thumbnails
Stereo Recording a circular ensemble-054e1a55-4dd7-4231-88e8-1eaefd422538.jpg  
Old 26th December 2018
  #11
RPC
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Agree - spaced omnis or back-to-back (sub)cardioids. (I find that back-to-back cardioids can give too low a level to the performers in the "middle.") In the case of omnis, if the ensemble is loud enough smaller diaphragm mikes (Earthworks, DPA 4007/4060) will minimize timbre changes. If using directional mikes, avoiding large diaphragm (1") will help for the same reason - Soundfield is ideal if you have access to one.
Old 26th December 2018
  #12
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i'd use a soundfield and downmix from 5.0 to stereo.
Old 26th December 2018
  #13
I have found omnis to work best in this situation. I will almost always use spot mics as well for more control.
Old 26th December 2018
  #14
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I'd at least consider arranging a pair of mics like they're overheads on a drum kit.
Old 27th December 2018
  #15
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Many thanks for so much good advice. I really might check out several options simultaneously and choose what fits best.

Nobody here seems to have experience or be thrilled with this double ORTF with four hypercardioids presented by Schoeps in that paper I quoted...

Would be Sennheiser Ambeo VR or Rode NT-SF1 good enough for acoustical ensemble recording? (Soundwise and noise...?)
I have no access to Soundfield mic and it's to expensive for to buy one...
Old 27th December 2018
  #16
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Quote:
Originally Posted by rojaros View Post
...Nobody here seems to have experience or be thrilled with this double ORTF with four hypercardioids presented by Schoeps in that paper I quoted...

Would be Sennheiser Ambeo VR or Rode NT-SF1 good enough for acoustical ensemble recording? (Soundwise and noise...?)
I have no access to Soundfield mic and it's to expensive for to buy one...
the schoeps ortf 3d system sounds great but not necessarily if downmixed to front oriented stereo - maybe for quad but who's still into that?!
i got a chance to use it on several occasions and it's for sure one of the best ways to get the .4 channels for ambeo.

cannot comment on the sennheiser or rode; even the least expensive soundfield has lower noise though and performs pretty well imo.

fancy checking out mine? when are you going to record and where are you based? i'm in basel, switzerland...
Old 27th December 2018
  #17
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Quote:
Originally Posted by deedeeyeah View Post
the schoeps ortf 3d system sounds great but not necessarily if downmixed to front oriented stereo - maybe for quad but who's still into that?!
i got a chance to use it on several occasions and it's for sure one of the best ways to get the .4 channels for ambeo.

cannot comment on the sennheiser or rode; even the least expensive soundfield has lower noise though and performs pretty well imo.
I wasn't meaning the full ORTF 3d system but rather what they called "Fig. 3: Four-channel "ORTF Surround" system; four supercardioids, 10 / 20 cm spacing, 80º / 100º angles"

it's described and photographed (Fig.3.) somewhere in the middle of that paper. It's a 4 channel system as far as the recording goes. The "full" ORTF 3d uses 8 channels.

Thanks anyway...
Old 27th December 2018
  #18
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Quote:
Originally Posted by rojaros View Post
I wasn't meaning the full ORTF 3d system but rather what they called "Fig. 3: Four-channel "ORTF Surround" system; four supercardioids, 10 / 20 cm spacing, 80º / 100º angles"

it's described and photographed (Fig.3.) somewhere in the middle of that paper. It's a 4 channel system as far as the recording goes. The "full" ORTF 3d uses 8 channels.

Thanks anyway...
sorry for using the wrong 'schoeps terminology': i was actually referring to the 4-capsule double ortf-array...

nevertheless, the problem remains: regardless of panning/amplitudes/eq shaping, it does not fold down to stereo very well. in order to do this, a system imo either needs to be coincident (soundfield) or then capsules facing towards the back/edges need to be at some distance and be spaced to pick up less correlated sound. one can use some efx to mimic this though...
Old 27th December 2018
  #19
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Simmosonic's Avatar
 

Quote:
Originally Posted by rojaros View Post
Nobody here seems to have experience or be thrilled with this double ORTF with four hypercardioids presented by Schoeps in that paper I quoted...
I think the Schoeps set-up shown in Figure 3 is very clever, and provides a 360° coverage in four stereo quadrants (Left Front/Right Front, Left Rear/Right Rear, Left Front/Left Rear, Right Front/Right Rear). This is probably great for four channel reproduction, but it’s not going to fold down nicely to stereo if placed within a circular ensemble. Here’s why...

If you were to take the front L mic (Left Front) and the rear L mic (Left Rear) and mix them together to create the left channel of a stereo mix, you’re essentially summing the Left Front/Left Rear stereo pair to mono. All sound sources that exist inside that quadrant and are captured by those two mics will now appear hard left, which immediately suggests it’s not a great idea for recording within a circular ensemble. Likewise for the right channel of a stereo mix; all sounds captured by the Right Front/Right Rear pair will appear hard right in the stereo image. And that’s without considering phase issues...

Sound sources that exist within Left Front/Right Front quadrant, and Left Rear/Right Rear quadrant, will be spread across the stereo image, but everything else will be hard left or hard right, and possibly with some comb filtering.

Last edited by Simmosonic; 27th December 2018 at 03:53 PM..
Old 27th December 2018
  #20
Quote:
Originally Posted by rumleymusic View Post
I have found omnis to work best in this situation. I will almost always use spot mics as well for more control.
Likewise. And, as Brent Hahn suggested above, with the omnis pointing down over the center of the ensemble like drum overheads.
Old 27th December 2018
  #21
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Quote:
Originally Posted by lukedamrosch View Post
Likewise. And, as Brent Hahn suggested above, with the omnis pointing down over the center of the ensemble like drum overheads.
Omnis don't "point," but otherwise, yeah.
Old 27th December 2018
  #22
Quote:
Originally Posted by Brent Hahn View Post
Omnis don't "point," but otherwise, yeah.
Assuming a single-diaphragm pencil omni with a typical high-frequency response which becomes more directional towards 180-degrees off-axis. Hence, an orientation which is symmetrical with respect to the performers seems prudent. Apologies for any vagueness.
Old 27th December 2018
  #23
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Quote:
Originally Posted by lukedamrosch View Post
Assuming a single-diaphragm pencil omni with a typical high-frequency response which becomes more directional towards 180-degrees off-axis. Hence, an orientation which is symmetrical with respect to the performers seems prudent. Apologies for any vagueness.
:-)
Old 27th December 2018
  #24
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Quote:
Originally Posted by deedeeyeah View Post
sorry for using the wrong 'schoeps terminology': i was actually referring to the 4-capsule double ortf-array...

nevertheless, the problem remains: regardless of panning/amplitudes/eq shaping, it does not fold down to stereo very well. in order to do this, a system imo either needs to be coincident (soundfield) or then capsules facing towards the back/edges need to be at some distance and be spaced to pick up less correlated sound. one can use some efx to mimic this though...
OK, just wanted to make sure we're talking about the same array.

I see your argument about the correlations and necessity of more spread array.

What about a pair of two NOS pairs on diagonals and with a quadratic spread of 30 cm each side?

I have been also considering the 'overhead' approach with two omnis or wide cardioids, too, but the ceiling in the recording room s qite low, si I'd bee close to the ceiling with the back sides of the microphones - that doesn't appear a good idea to me.
Old 27th December 2018
  #25
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Quote:
Originally Posted by rojaros View Post
I have been also considering the 'overhead' approach with two omnis or wide cardioids, too, but the ceiling in the recording room s qite low, si I'd bee close to the ceiling with the back sides of the microphones - that doesn't appear a good idea to me.
If the ceiling is really low, you can try putting your omnis right up against it. Then sound can't reflect off the ceiling into the mics, and it's like the ceiling isn't there. FWIW, this works with piano lids, too.
Old 27th December 2018
  #26
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Quote:
Originally Posted by rojaros View Post
OK, just wanted to make sure we're talking about the same array.

I see your argument about the correlations and necessity of more spread array.

What about a pair of two NOS pairs on diagonals and with a quadratic spread of 30 cm each side?

I have been also considering the 'overhead' approach with two omnis or wide cardioids, too, but the ceiling in the recording room s qite low, si I'd bee close to the ceiling with the back sides of the microphones - that doesn't appear a good idea to me.
i do not consider any identical stereo mic arrays positioned differently and aiming in different directions to be well suited for downmixing to stereo (and hardly ever use stereo spots or spaced 4-mic arrays for this reason).

if not using a soundfield, i'd proably use an m/s system for front pickup and a (widely) spaced a/b pair (of directional mics) for rear pickup: this way, the front system can be used as wide or narrow as wanted while the rear signals get fully panned to each side.

Last edited by deedeeyeah; 27th December 2018 at 06:56 PM.. Reason: edited twice for clarification
Old 27th December 2018
  #27
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Quote:
Originally Posted by deedeeyeah View Post
i do not consider any identical stereo mic arrays positioned differently and aiming in different directions to be usefull for when it comes to downmixing to stereo (and hardly ever use stereo spots for this reason, unless both systems are coincident pairs).

if not using a soundfield, i'd proably use an m/s system for front pickup and a widely spaced a/b pair for rear pickup: this way, the front system can be used as wide or narrow as wanted while the rear signals get fully panned to each side.
OK, that sounds like an option. On the other hand, couldn't one have two near coincident arrays on front and back each and than work with some kind of mid side stereo processing in mixing?
Old 27th December 2018
  #28
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Don't record a circle as such

Divide them into hemi spheres and place a sum and difference pair of fig 8s in the centre

Ensure they are all in field and critical distance and let them self balance

This works a treat

Roger
Old 27th December 2018
  #29
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Quote:
Originally Posted by rojaros View Post
...couldn't one have two near coincident arrays on front and back each and than work with some kind of mid side stereo processing in mixing?
in my experience, it's possible to tweak/fake the behaviour of an m/s array to some degree by using capsules other than cardioid and fig8 (say two cardioids for sides and wide cardioid for mid) yet all mics need to be coincident.
Old 27th December 2018
  #30
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Quote:
Originally Posted by Rolo 46 View Post
Don't record a circle as such

Divide them into hemi spheres and place a sum and difference pair of fig 8s in the centre

Ensure they are all in field and critical distance and let them self balance

This works a treat

Roger
Never worked with a sum and difference pair of figure eight. Could you please elaborate? Sounds like I'd need 4 figure eights. I just acquired a pair of Sennheiser MKH 30, but I could also provide a matched pair of AKG C414 XLS... would that do?

How do I have a sum and a difference pair?

Sorry for maybe a stupid question...

Last edited by rojaros; 28th December 2018 at 10:34 AM.. Reason: Mistake changed omnis to figure eights
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