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Gear / Technical Help => Microphones & Setup => Topic started by: jnorman34 on November 04, 2008, 02:21:34 PM
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When using a spaced pair of omnis, how do you determine the best amount of separation based on how far you are away from the sound source, how large the group is, etc? Much of what i read suggest quite large spacing, like 6 feet, but in my studio, when i do a piano/violin duo or similar, i find that even 2 feet apart results in an overwide LR playback, too much separation, hole in the middle thing. What do youse guys use? danke.
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Good question. I'm interested to.
This is the rule I know, when you're outdoor use omni in X/Y pattern but a lot of the rig photos look like they are right next to each other and not necessarily x/y so what gives? Whats the advice?
peace,
sean
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i've always enjoyed results from a 3' split but that is in a particular room that sounds great where i'm about 20 ft from the stage.
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Here's a blatant self-reference to a post of mine (http://taperssection.com/index.php/topic,106630.msg1423748.html#msg1423748) on things to consider when running spaced omnis. Here's another (http://taperssection.com/index.php/topic,93017.msg1239775.html#msg1239775) in a seperate thread. And yet another. (http://taperssection.com/index.php/topic,85607.msg1139141.html#msg1139141) Feel free to read the other posts in those threads too. :P
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Here's a blatant self-reference to a post of mine (http://taperssection.com/index.php/topic,106630.msg1423748.html#msg1423748) on things to consider when running spaced omnis. Here's another (http://taperssection.com/index.php/topic,93017.msg1239775.html#msg1239775) in a seperate thread. And yet another. (http://taperssection.com/index.php/topic,85607.msg1139141.html#msg1139141) Feel free to read the other posts in those threads too. :P
I recently recorded some thunder at 50 cm (~20")...
http://www.freesound.org/samplesViewSingle.php?id=62278
http://www.freesound.org/samplesViewSingle.php?id=62275
Worked for me :)
(http://www.digifishmusic.com/public/images/Freesound_ThunderRig.jpg)
then again any old baffle separated by about 6" is good too...this one is an improvised baffle and I think it did the trick...
http://www.freesound.org/samplesViewSingle.php?id=57668
(http://www.digifishmusic.com/public/images/Freesound_LakeEacham.jpg)
like Mr Gutbucket said, whatever works. I am however very partial to baffled omnis.
digifish
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When using a spaced pair of omnis, how do you determine the best amount of separation based on how far you are away from the sound source, how large the group is, etc?
Unbaffled spaced omnis only record phase differences between their positions. While the phase cancellations provides a good feeling of spaciousness, they really don't provide provide any detailed spatial information.
There's a better way to do spaced omnis: use a baffle -- either a Jecklin or a Schneider Disk. Using either one, you'll get the all the omni features we love (a very flat frequency response, much better bass response and much better resistance to wind and handling noise than cardioids), and strong (really strong) location cues.
You can see pictures of both Disks on our Web site. You can also see a picture of a Jecklin Disk on the Josephson site.
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When using a spaced pair of omnis, how do you determine the best amount of separation based on how far you are away from the sound source, how large the group is, etc?
Unbaffled spaced omnis only record phase differences between their positions.
So arrival time is not encoded by a spaced omni?
digifish
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Phase is arrival time (in a sense), but the question then becomes can our brain/ear systems make sense of the recorded phase information to decode spatial location, and the answer is generally no. Especially when played back over a stereo playback system. You'll hear the "comb filtering", and that's what we perceive as spatial info.
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I'm another proponent of baffles. Omnis can work work from very far back if you understand why and how to apply them. Take all opinions with a grain of salt, read, digest, experiment and follow your ears.
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jnorman wrote:
> Much of what i read suggest quite large spacing, like 6 feet, but in my studio, when i do a piano/violin duo or similar, i find that even 2 feet apart results in an overwide LR playback, too much separation, hole in the middle thing.
Many people seem to assume that you couldn't possibly get adequate stereo "separation" from omnidirectional microphones unless they are rather wide apart. But as you've found out, that's a misconception. I really don't know where it comes from, except to note that strangely, some people adhere to "visually driven" theories about audio even when they don't work.
A baffle of some kind can often help, as people here are suggesting; to me the best sounding type seems to be a sphere with the diaphragms of the microphones even with its surface. But even without a solid object between the microphones, you usually don't need wide spacing for good stereo pickup. And I would say that the spacing should be kept as narrow as possible consistent with good overall balance, to hold the "hole in the middle" effect to a dull roar.
--best regards
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I rarely space omni's wide than ~18". I use the Williams charts to determine the separation and follow his techniques. They work quite well. He has built upon the research of others. As this is all physics I do not feel the need to reproduce experiments of others. Instead I follow their guidance. There are some who like wider spacing. Williams' papers are on this board in this sub-forum as a sticky at the top of the sub-forum page.
I have a Jecklin which I need to adapt to working with my current preferred omni's.
Cheers
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Good question. I'm interested to.
This is the rule I know, when you're outdoor use omni in X/Y pattern but a lot of the rig photos look like they are right next to each other and not necessarily x/y so what gives? Whats the advice?
I'm sorry, but this makes absolutely no sense to me. If you are using omnis in an XY pattern, you will get no spacing whatsoever with the omnis and the sound will be mono, given the nondirectional nature of omnis.
For outdoor shows and festivals, I like spacing my omnis about three to four feet apart; more than that and I get a hole in the center. I don't use a J-disc, but then again, I am an extraordinarily lazy taper.
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I usually split 3'.
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You might also have a look at Ray Kimber's IsoMike:
http://www.isomike.com/
His recordings are quite fine.
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That one is tough on sightlines! I met Ray last spring and talked with him about his IsoMike rig. I keep thinking about how to incorporate a baffle with a larger mic spacing between mics to set-up farther back in the room. As the mics get further away from the baffle the baffle must increase in size to keep the same shadowed angle from mic to baffle edge. The IsoMike does that by scaling everything up to gigantic proportions. I've considered trying two small baffles separated from each other, with the mics just outside of them. Imagine placing mics the usual distance from a jecklin disk, then splitting that disk down the center like an Oreo cookie and moving the two halves apart. Secondarily as a second variable, one could angle the baffle faces forward a bit as well.
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Dave Satz wrote:
A baffle of some kind can often help, as people here are suggesting; to me the best sounding type seems to be a sphere with the diaphragms of the microphones even with its surface.
Have a look at the Schneider Disk and you'll see that it looks like a sphere embedded in a Jecklin Disk. I like the mics to be an inch or so off the surface of the sphere.
I use the Schneider with a pair of DPA 4003s for smaller groups like choirs up to 30 or 40 voices, and bands -- it provides really excellent location cues. For wider sources like orchestras and larger choirs, I find the Jecklin does a better job.
If you'd like to hear a sample, let me know where to upload it.
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Good question. I'm interested to.
This is the rule I know, when you're outdoor use omni in X/Y pattern but a lot of the rig photos look like they are right next to each other and not necessarily x/y so what gives? Whats the advice?
I'm sorry, but this makes absolutely no sense to me. If you are using omnis in an XY pattern, you will get no spacing whatsoever with the omnis and the sound will be mono, given the nondirectional nature of omnis.
For outdoor shows and festivals, I like spacing my omnis about three to four feet apart; more than that and I get a hole in the center. I don't use a J-disc, but then again, I am an extraordinarily lazy taper.
I have never heard of using omni's in an X-Y array. There may be a reason for that. Omni's are used as spaced arrays, A-B. Sometimes the distance between A and B is great. The greater distances are apparently more common here than in Europe. I have a mfr's mic bar for his omni's and the widest they go is 18 - 20". I would assume he wants his mics to sound as good as possible and would offer a wider bar if it would do that. YMMV. 8)
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You might also have a look at Ray Kimber's IsoMike:
http://www.isomike.com/
His recordings are quite fine.
It's insane! :)
I love it when people take their ideas to extreme...
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if im close enough (within 5'of the stage), i run omnis healey method (17 cm, 180* from each other), and have gotten great results.
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A foot to about 2