Topic: How split do split omnis need to be?

[Gutbucket]

A baffle (such as a Jecklin disk) is one way of making an omni-microphone behave less omnidirectionally.  The polar behavior of a baffled omni pair is more complicated than either non-baffled omnis or directional microphones.  A baffle can be used as a way to reduce the spacing which would otherwise be needed between two omnis used as a stereo pair. If you use a baffle, you won't want as much spacing between omnis as you would without a baffle.

For physical geometry reasons the omni microphone needs to be relatively close to the baffle for the baffle to be effective in changing the pattern of the omni, unless the baffle is very large (google ISO-mic for a gargantuan example). Think of it as providing a shadowing effect at high frequencies.  The physical size of the baffle also determines how low in frequency the directionality is effective.  Low frequency sound with wavelengths similar to the dimensions of the baffle just wrap around it and aren't "shadowed" like higher frequency sounds.

One way of using smaller baffles with wider microphone spacings could be to two separate baffles, each one relatively close to its own microphone.  Not so practical on a microphone stand though.

[lsd2525]

I suggest trying X/Y in the middle first if you can rig that.   If that's a PITA you can always try just the single forward facing cardioid in the center. But you'll have that extra channel so you may as well use it, and X/Y is pretty much as non-problematic mixing-wise as the single forward facing cardioid (although you could use that 4th channel for a SBD feed).

If it were me, I'd point one cardioid directly forwards and the other one backwards, spaced about 20" front/back between 6' spaced omnis.  But that's another step along the path away from trusted taper setups, through the looking-glass down into the rabbit hole. 

If the X/Y setup or single cardioid works well for you, I'll point you to a few threads explaining why you might want a backwards facing cardioid.

I've been considering adding a coincident figure-8 to the single center facing cardioid of my surround recording setup based upon this same technique, to form a Mid/Side coincident pair in the center providing similar center width adjustment as a pair of coincident X/Y cardioids.  Depending on what you are recording and the situation, the X/Y pair may be more useful to you than the rear facing cardioid.

If I could get a board of who I'll be taping I take that and the omni's and leave the cards at home

[voltronic]

For physical geometry reasons the omni microphone needs to be relatively close to the baffle for the baffle to be effective in changing the pattern of the omni, unless the baffle is very large (google ISO-mic for a gargantuan example). Think of it as providing a shadowing effect at high frequencies.  The physical size of the baffle also determines how low in frequency the directionality is effective.  Low frequency sound with wavelengths similar to the dimensions of the baffle just wrap around it and aren't "shadowed" like higher frequency sounds.

This makes perfect sense.  What doesn't make sense (to me) is Jecklin's revised OSS specs of a 36cm disc with mic spacing of 35cm.  I'm sure Jurg Jecklin knows a hell of a lot more than I do, but it would seem to me that at that spacing the baffle is going to be far less effective, unless you make it enormous like the Kimber Iso-Mike you referenced.  I really wonder if the revised Jecklin would sound that much different than spaced omnis, unless you're very close to the source.  http://www.sengpielaudio.com/JecklinDisk.pdf 

[lsd2525]

I suggest trying X/Y in the middle first if you can rig that.   If that's a PITA you can always try just the single forward facing cardioid in the center. But you'll have that extra channel so you may as well use it, and X/Y is pretty much as non-problematic mixing-wise as the single forward facing cardioid (although you could use that 4th channel for a SBD feed).

If it were me, I'd point one cardioid directly forwards and the other one backwards, spaced about 20" front/back between 6' spaced omnis.  But that's another step along the path away from trusted taper setups, through the looking-glass down into the rabbit hole. 

If the X/Y setup or single cardioid works well for you, I'll point you to a few threads explaining why you might want a backwards facing cardioid.

I've been considering adding a coincident figure-8 to the single center facing cardioid of my surround recording setup based upon this same technique, to form a Mid/Side coincident pair in the center providing similar center width adjustment as a pair of coincident X/Y cardioids.  Depending on what you are recording and the situation, the X/Y pair may be more useful to you than the rear facing cardioid.

So if I used a front and rear facing cardorid, I would want to pan both to center, correct?

[chk]

experiment! while the conventional wisdom is that omni's have to be split by at least a foot or two (and generally for good reason), the "Healy" or "critically spaced omni" technique can yield pretty nice results.  Basically aim the caps outward from each other 180 degrees, spaced approx 7" apart.   Here's a recording I just made using this tactic onstage, and i was reasonably pleased.  https://archive.org/details/nm2014-06-12.flac16.onstageCA11Omni

[Gutbucket]

If I could get a board of who I'll be taping I take that and the omni's and leave the cards at home

That combination works really well.
Upfront clarity and presence and detail filling the center of the image from the SBD.
Open, enveloping stereo immersion and ambience out to either side from the omnis.

So if I used a front and rear facing cardorid, I would want to pan both to center, correct?

Balance the front three channels first, that’s +90% of everything. Start with the omnis, balance them and eq if necessary.  Then bring up the level of the forward facing cardioid until you find a good blend of all three.  You can do some eq on the forward cardioid too if necessary.  Don't worry about the bottom end of the cardioids, the omnis will take care of that completely, what is important in the cardioids is clarity.  Play around with the level of the center forward facing cardioid in the mix.  Sometimes a similar level to the omnis works best, sometimes less, sometimes more.  You will hear it will "click" into place sonically when the balance is right.  Sometimes it works with the center mic at a few significantly different levels it's just a matter of choosing which is best. 

Once the front three channels are balanced, you can season things by bring in a touch of the rear facing microphone.  In a stereo mix it provides some natural openness, ambience and crowd reaction.  Often just enough level to make things sound natural, barely noticeable except in its absence.  For a stereo mix I may automate the level to bring it up higher between songs when the crowd reaction and excitement is strong.  Simplest is just to pan it center, but some pseudo-stereo techniques can spread it out (ideally it is decorellated in the left and right channels so it spreads out to both sides and is not centered in the mix).

In a surround mix the rear facing cardioid forms the surround channel and can be used at a higher level without conflicting with the front.  It’s duplicated and routed to each of the surround speakers (and optionally decorellated between each surround speaker channel like using it with the 2-channel mix, though that is less important).


But I suggest the X/Y cardioid center to start.  Bring the X/Y up after the omnis are balanced, with both cardioids panned to the center (or collapsed to mono using a stereo width panning control, which is the same thing), adjust their level as mentioned above, then play with increased center width by panning each outwards to left and right (or by increasing the stereo width on the panning control, same thing) until you get a nice even image a blend across the playback stage between speakers.

[Gutbucket]

What doesn't make sense (to me) is Jecklin's revised OSS specs of a 36cm disc with mic spacing of 35cm.

There was alot of Jecklin talk around here  6 or 8 years ago.  Everyone was building their own baffles of various configurations.  I always liked more spacing than the original Jecklin specification because that produced more significant stereo information at lower frequencies and just sounded better to me.  The revised specs seem more in-line with my preference at least.  I build a very large oval one but never worked up the cajones to fly it.  Plenty of photos and threads here at TS if you do a search.

I found the Jecklin-disk thing worked best for me up close, like stage-lip or onstage.  Works great in the center of a circle of musicians jamming.

"Healy" or "critically spaced omni" technique

Sort of like Jeklin without the disk.  I think Healy just didn't have a disk.     I've heard he did that for adding on-stage sound to the IEM mix so the band members could commuinicate with each other when the dead first stated using IEMS.  Sort of a quasi-binarual thing without the headbaffle.  Larger diameter diaphram omnis probably work best for that since they get a bit directional at high frequencies and I think that's what he used.

Yes! Experiment.  It's the only way to really figure it all out.

[Ultfris101]

Motivated by Gutbucket's comments in threads like this and some discussion via PM I'm starting to play around with split omni/hypercardiod center combinations when I'm recording outside and like it a lot. For one it's a simple configuration to setup, especially the directly forward and backward facing cards. No angles to measure!!! I also like the way it looks. I should post something in Rig Pics.

I realized during my first attempt that it would have been nice to have a stereo pair that I understand to compare to the omni/hyper mix but that's another two channels, batteries, etc to fuss with. An X/Y pair is an interesting idea for the center to provide both.

This is a timely thread as I'm starting the planning for my next festival outing in mid July.

For a bar I too did exactly what Chuck did based on the same thread: http://taperssection.com/index.php?topic=161914.0

Very easy. The fiberglass poles are a good idea if you have mini mics like 853's or 4061's or something which I do but I also wanted to use Schoeps and AKGs so the aluminum made sense. Also, you can slide rapid adapters over the aluminum and get easily adjustable width if you need it for something. I did that so I could pull my mics in under an umbrella if necessary since it was threatening rain.

[Gutbucket]

I realized during my first attempt that it would have been nice to have a stereo pair that I understand to compare to the omni/hyper mix..

Yep, I find the only way I can make reliable decisions on new setups is through comparison.  Please let me know how this stuff works out for you.

[T-90]

Gutbucket has never split any omnis, don't let him fool ya 

[voltronic]

What doesn't make sense (to me) is Jecklin's revised OSS specs of a 36cm disc with mic spacing of 35cm.

There was alot of Jecklin talk around here  6 or 8 years ago.  Everyone was building their own baffles of various configurations.  I always liked more spacing than the original Jecklin specification because that produced more significant stereo information at lower frequencies and just sounded better to me.  The revised specs seem more in-line with my preference at least.  I build a very large oval one but never worked up the cajones to fly it.  Plenty of photos and threads here at TS if you do a search.

I found the Jecklin-disk thing worked best for me up close, like stage-lip or onstage.  Works great in the center of a circle of musicians jamming

So for distant, you only do spaced?  I was going to start using a baffle to make things more compact / less obtrusive but have had great results with wide (probably way too wide) spaced pairs in the past.

[Gutbucket]

I found the Jecklin-disk thing worked best for me up close, like stage-lip or onstage.  Works great in the center of a circle of musicians jamming.

So for distant, you only do spaced?  I was going to start using a baffle to make things more compact / less obtrusive but have had great results with wide (probably way too wide) spaced pairs in the past.

Pretty much.  From farther away more spacing on the omnis works well, as long as you can rig it practically and block it, without blocking the sightlines of everyone behind you.  It's only too wide if the middle gets weak and wishy-washy, but the single microphone or pair in the center takes care of that.  An omni works in the middle too, but a directional sort of zooms in on the forward facing direction, seemingly decreasing the apparent sonic distance.     

A Jecklin is pretty big and obvious up there, especially from slightly off to the side.  Easier to get away with on stage than up on a stand in my experience, but of course it depends on how bulky the A-B omni spacing setup is.  Jecklin also sort of eats highs, requiring a healthy eq correction at a distance to balance that.  Its more mono-ish bass quality doesn't work for me from farther back, its quite different sounding than wide omnis.       

[Gutbucket]

Gutbucket has never split any omnis, don't let him fool ya 

T-90 has never left idle message bomb surprises on recordings during set breaks. 

T's one of the few who was there the first time I stuck a pole in the air at an outdoor amphitheater, changing spacings and scribbling notes between sets (3' was best ) with two 4060s on a telescoping TV antenna gaff taped to a painter pole stuck into the back of my chair.  And also one of the few I know who has taken up the miniature omnis on a TV antenna idea.  Smells like validation.

[lsd2525]

My dream of having the most ghetto rig at the show is about to become a reality.......

[hoppedup]

My dream of having the most ghetto rig at the show is about to become a reality.......

Only because I am now out of the ghetto rig game. I was the king.

FWIW I've run omnis at 12" apart at many shows either on-stage or directly in front of an acoustic duo, trio  or full band. Outdoors at greater distances from the stage I run a 3' split. I've been pleased with the results in both cases.

ETA: The first time I ran mics, I ran CA-14 loaner omnis on a 3' split on a homemade bar attached to a painter's pole. I cut the end off of a paint roller handle to use as a nut to secure the bar to the top of the paint pole. Then I just duct taped the pole to my camp chair and had my nephew sit in it to weigh it down.