Topic: Oddball microphone techniques - part 1

[Moke]

Mr Jecklin isn't actually much of a stickler for conformity at all.  I've corresponded with him about baffles and shuffling.  He has simply related what has worked for him, and actually modified his setup considerably over the years.

I think it's others reporting what he's done in an overly specified manor, reporting whatever the dimensions of his setup are as some sort of gospel instead of the more important concepts underlying them, just because that's so much easier than understanding and translating the underlying principles at work.  I feel it's somewhat similar to Tony Faulkner being branded with the oft-reported super-specific spacing of the "Faulkner Phased Array" (near-spaced parallel bi-directionals) which he himself dismisses in every interview I've ever seen or heard when hes asked about it.  He understands how things work and shifts things around until they do.  It's others who attempt to saddle what he does with exact measurements and other specifics.

All that said, tiny omni baffles most definitely qualify as odd-ball!

[edit] extra-credit for identification of the TS member in green in Mokes first photo above, but only to new member's here (say joined post 2010).  Hint- it's not Moke, and he doesn't live anywhere near him.

Lets just call it,... Monday Morning Surliness.

When I first read his works, his was entirely stringent.  That was back in the early-mid 90's at a time when I was having to repair the cancer stricken circuit board of my MKE2002 pair (circuit board peeling and lifting; eventually solved by point to point wiring). I was having to face the reality that my old binaural comanions were dying, and I started into looking into alternate baffled omni theories beyond HRTF/Binaural.
At any rate,... Moke might be a little surly this morning. Sorry to all.

[Moke]

Mini Baffle
This baffle is roughly the same size as a CD (slightly larger than a cd), only square. Why square? Because round is a PITA to mount, and I'm lazy. I'd rather listen to music than build a baffle.
The cables weave through the disc face to reduce cable tension, which also helps locate the mics to the face of the baffle, and keepping them there.

The mini baffle, in different profile angles, below

[heathen]

Thanks Moke!  Any chance you could share a sample of a recording made with that setup?

[Moke]

This is the handiest of my baffles.
This sort of started the quest to see how small you could go with a baffle.
I did this, and was astonished at the sound in the house; Sarge was where she was supposed to be in a binaural sense, the washing machine was grinding off in the distance to one side,.... 
I then went walkabout up this horsetrail, and across to a park, just recording a meandering walk.  It was a nature recording in a city'ish area. But, airplanes became pinpoint placed overhead, birds to left and right, cars whizzing by, all in glorious two channel stereo. I must've looked a bit odd, but,.. thats not that unusual. You ought to see me when I'm out dousing (water witching).

Plankton,... well, he displays the stealther attitude.

edit: fixing the autocorrect corrections.

[Moke]

Thanks Moke!  Any chance you could share a sample of a recording made with that setup?

Thats a challenge.
I've got to review the pictures, to see where to look for the files.
Let me say, that I settled on an 8" baffle, that I felt worked really well with my 4060 mini omni pair.

The WsP is long gone now, from my collection. But, its out there, I think, if you know that community.
I did, and still do, do far more recordings with my larger, but, still small scale baffle. That slightly larger baffle is 8", and I found that to be a really sweet size with the miniature omni pair.
I was searching for an image of my 8" baffled omnis, with a DPA 4028 sub-card over it as a three channel recording. The band had commandeered one of my pair of 4028 to be used as a close mic source for a very quiet intimate native american flute concerto premiere. They couldn't hear the flute over the backing ensemble. So, I volunteered one of my mics as that onstage close mic (direct to a small amp via my also onstage recording bag and Grace preamp).
At any rate, I ran three channels; two as baffled omnis, and one as a vertically aligned sub-card at 0º, hoping that maybe, some day, somebody as kind, wonderful, helpful, and a dear friend, like Gutbucket, might help talk me through a mix. (sucking up enough, Lee?)

[Gutbucket]

This raises a good point that we may all prefer somewhat different things, that real-world practicality is so often far more important than our ultimate preference based on sonics alone, and that we tend to stick with what has worked for us previously.

That a tiny baffle works perfectly well and is eminently more practical than a larger one plays directly into that.  Jecklin stuck with a 12" diameter baffle for a long time, simply because his first baffles were built around an old LP record.  He eventually found he preferred a slightly larger diameter baffle with a bit more spacing between the mics, but he was doing studio and orchestral recording where he had freedom of control and the ability to tweak the setup for subtleties, rather than taper recordings like we are doing where we don't have control and practicality trumps subtle acoustic niceties. 

I think Blumlien's original baffle was something like 8" in diameter (but thicker making it more head-like, although I'd have to check the patent to be sure) - so he's somewhat closer to the Moke-tiny-baffle-camp.   After all, Blumlien is mostly thought of as the father of coincidental microphone techniques.  At the opposite extreme, we've all seen photos of Ray Kimber's gargantuan ISO-Mic baffles which take a crane to lift.

I mostly gave up on typical J-disk baffles as being less than practical for the size I felt I wanted them to be for the effect I wanted to achieve.  Spacing tiny omnis further apart was easier for me, less intrusive, and gave me more of what I wanted from them, and flush-mounting them in small balls combined with spacing ended up serving a similar purpose in a more practical way. 

I've used columns, tree trunks, menus and other things as baffles.  Its the concepts behind them which are important, rather than the particulars of the baffles themselves.

..hoping that maybe, some day, somebody as kind, wonderful, helpful, and a dear friend, like Gutbucket, might help talk me througha mix. (sucking up enough, Lee?)

I owe you so much my friend. I originally came to TS asking about baffles back in 2006 and was immediately directed to you as resident expert!  More than happy to lend whatever expertise I can.

[Gutbucket]

A few comments on the Omni Cross and IRT Square configurations shown in that Sanken link of surround configurations-

These 4-channel configurations are common formats for recording ambiences.  The IRT Cross is especially popular for things like location sound used for broadcast or film since it is relatively compact.  It can be done using either cardioids with a bit more spacing or supercards with a bit less between each mic.   Consider that it is basically four DIN setups pointing in all four cardinal directions, sharing a microphone at each corner.  It has a bit more spacing than DIN to narrow the SRA of each pair to 90-degrees so that each imaging quadrant links with the next without excessive overlap or gap- this is the Williams Stereo Zoom thing, arrayed for seamless 360 degree coverage using four microphones.  For TV and film use the four channels are routed Front-Left/Front-Right/Surround-Left/Surround-Right, reserving the center channel for dialog and main channel content.

I consider the Omni Cross to be similar to Decca Tree, just rotated 45degrees, with a rear microphone added, and reassigning the channels from Front-Left/Front-Right/Surround-Left/Surround-Right to Left/Center/Right/Back.  Call that a Decca Diamond setup if you like.  That's the four channel setup I ran for years using ball baffles on the omnis partly as a way to minimize the need for excessive spacing.  I initially tried to space all the mics about a half-meter out from center, so both L/R and C/B spacing was about a meter in total.  Center/Back omni spacing often ended up being less than that as determined by practical considerations.

I found I wanted more left/right spacing, didn't need or especially want much spacing of the center mic forward of the left/right pair, and typically ended up not with a right-triangle shaped diamond configuration but rather a flatter diamond shape which was much wider than it was deep.  That played into spacing the L/R omnis 1.5 to 2 meters apart and changing the center and back mics to directional mics only spaced minimally fore and aft.  That then evolved into the OCT derivatives with the addiion of left/right facing supercards placed between the center and omnis.

I think of all these arrays as being linked by the same underlying acoustic principles.  So when I look at my oddball OCT+ array, I also see at it's core a 4-channel IRT cross rotated 45 degrees with it's channels reassigned, in a way similar to rotating an Omni Square configuration by 45 degrees to form a Decca Diamond.  I also see a simple 2-channel wide spaced omni pair, and a wide omni plus directional center three-microphone configuration.  I find a certain engineering beauty, elegance and welcome redundancy in the common aspects shared between these arrays and finding ways of combining them in this way without conflict.

[Moke]

Thanks Moke!  Any chance you could share a sample of a recording made with that setup?

http://taperssection.com/index.php?topic=183411.msg2239027#msg2239027

5" mini omnidirectional baffle sample
https://archive.org/details/Miniature5BaffleDPA4040

Sample:
All acoustic string quartet and lute soloist
DPA 4060 mini omni pair -> DPA MMA6000 power -> Grace Lunatec V3 48khz ANSR ->  Sony PCM-M1 Dat Oade 7-Pin digi-in
The mics are fairly low, at a level equal to the seated Lute players instrument.

I feel that this quality is very evident:
The string quartet is cleanly placed in the aural image as being in a semi-circle around the Lute, who is centered to the ensemble; and the mic array is centered to all of that.
The bass is well placed to the right, but, does bleed over a bit (there are actually two bassists in this quartet, one deeper into the semi-circle than the other.). It does retain its proper positioning in the captured aural imagery.

[heathen]

Moke, I think that recording sounds great.  I'm not much of a classical music guy (I like it well enough, but rarely listen to it), but I've listened to this a couple times already.  I definitely want to try out a small baffle like that now (though sadly I don't have access to recording anything other than PA shows...which seem to be mostly mono anyway).

[2manyrocks]

Maybe try a local college because they tend towards classical.

What practical difference does it make whether the baffle is square vs round?  Square much easier to make and mount just as Mike said.

[Gutbucket]

^ not much.  What is most significant is the area of the baffle, the reflectivity of the surface and how far the mics are mounted from it.  With a small baffle, the mics need to be closer to the surface to keep it effective.

[thatjackelliott]

Two omnis and a little baffle. Neat idea. For music festival application I wonder how this would work compared with the setup I'll be using at our next event?

What I'm Gonna Do: Use a M-S configuration on the stage lip with a bipolar mic for Side and an omni for Mid + a time-aligned mono feed from the SB to bolster the omni Mid signal with detail and fill in the stuff that isn't loud onstage but boosted in the PA.

But What I Could Do: Use this mini-baffle setup + the time-aligned feed from the SB.

Mono-compatibility is essential for the broadcast (our FM stereo generator is turned off right now), and both the M-S setup and this dual-omni/mini-baffle setup provide that.

[Gutbucket]

^ You'll get best mono-compatibility the way you are doing it (Mid/Side, using only the mid for broadcast), along with more full-frequency-range stereoness in your stereo recordings, where you can bias the Mid/Side to L/R conversion matrix towards as much bidirectional Side as is necessary.  And that's likely to be advantageous given the fully mono PA feed.

Moke's IMO excellent sounding sample was made in what is probably the optimal situation for such a mini-baffle, or pretty much any baffled omnis.  That is, relatively close in to complex acoustic instrument sources.  The stereo image heard live from that perspective in the room will be wide due to the proximity to the group, so a mic setup which maximizes or otherwise emphasizes stereo width is unnecessary.  The stereo interest is mostly in the midrange and higher, and the relatively minimal stereo width at low and lower mid-range frequencies serves to solidify the overall image.  The omnis nicely capture all the detail, nuance, and frequency extension of the un-amplified acoustic instruments as well as a very natural sounding ambiance, and there is no audience or room noise problems to worry about.  That kind of situation is ideal for baffled omnis at the stage-lip or on-stage.

Two quite different situations to my way of thinking, except for being on-stage/stage-lip.

[Moke]

Moke, I think that recording sounds great.  I'm not much of a classical music guy (I like it well enough, but rarely listen to it), but I've listened to this a couple times already.  I definitely want to try out a small baffle like that now (though sadly I don't have access to recording anything other than PA shows...which seem to be mostly mono anyway).

In louder music, you'll likely find a bit larger of a baffle size to be more fitting.  High amplitude bass can/will overwhelm a smaller baffle.  In my time in playing around with baffles, I found that I really liked a 8" baffle, and mics small enough to be flexible in placement in relation to the disc face; IOW, to be scaled correctly for the smaller baffle. Smaller baffle, closer to disc face spacing.
I still carry the 5" baffle in my recording kit, but don't use it much.

[Moke]

..hoping that maybe, some day, somebody as kind, wonderful, helpful, and a dear friend, like Gutbucket, might help talk me througha mix. (sucking up enough, Lee?)

I owe you so much my friend. I originally came to TS asking about baffles back in 2006 and was immediately directed to you as resident expert!  More than happy to lend whatever expertise I can.

Lets test your patience :)

I've been looking for this recording since I mentioned it. Its not exactly as I remember it (from 2009), in terms of mic placement, but its close.  I've done this setup a few times now, and later eforts were with better time alignment than these images.  The center mic is about 5 or 6" in front of the omnis, as this was the only way that I could get it in close to the baffle, and centered, for this impromptu rigging.
Rigged as three mic recording:
DPA 4060 baffled omni stereo, with mics intentionally closer to baffle face for isolation (in hopes of doing something like a figure-eight response, and possible m/s rendering in post-edit).
DPA 4028 compact sub-card at 0º

I've found that if I invert the polarity of either 4060, that the sound opens up.
What seems to be happening, without the phase inversion, is the the 4028 is bringing the whole right side of the ensemble to center, and leaving the left side of the ensemble in a more stereo width spread. It seems to phase cancel the right side to a degree, bringing it to center.
If I invert phase on either 4060 track, one one track only, it opens back up again, bringing full stereo width, and proper right channel placement.

So, to set these tracks up for a quasi-m/s mix, which 4060 track should be phase inverted? It doesn't seem critical for a generalized mix, so, lets get it right for a possibe m/s rendering.
problem for me, and a proper m/s...
I'm a computer klutz, and, doing a proper m/s rendering is eluding me.  YOu've mentioned setting something like this up for a quasi-m/s rendering.
How? please and thank you.