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Why avoid omnis in deficient rooms?
Old 24th January 2013
  #1
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Why avoid omnis in deficient rooms?

I have seen mentioned over and over the idea that omnis are really only suitable in a good room. It seems that the typical mics used in less desirable rooms are cards, say in ORTF.

Might someone be able to explain the reason for this guiding principle?

In my (erroneous) thinking, I would tend to think that, when the reverberation is less than desired, I would want to get as much of the room as possible to capture what little exists. Hence, I would think that omnis would be preferred over cards, since the cards would reduce the effect of the room, thus reducing the reverberation that I might otherwise capture with the omnis.

Obviously, I am misunderstanding something basic.

Thank you for any comments.

Regards,

DG
Old 24th January 2013
  #2
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Kaoz's Avatar
No room sound is better than bad room sound.
Old 24th January 2013
  #3
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boojum's Avatar
Plush often points out that we record the room. When it is less than stellar lost as much of the room as you can. Cards, close in, will do that. And while you are doing that think about a really regal venue where the omnis will work really well. Then you can use the cards for spots.
Old 24th January 2013
  #4
My best advice would be to try it for yourself, and then you will instantly understand.

Some thoughts that come to mind:
Don't mistake a "dry" room for a "bad" room. Bad rooms often have, or cause, bad sonic coloration. More often than not, this is true of smaller rooms that tend to have peaky modal responses, but there are some big rooms that don't sound particularly good either. Once this room sound gets in your recording, there is not much you can do about it.

By using a directional mic, you have better control over the direct-to-reverberant sound in the recording. If the room sounds bad, better to get as much direct sound as you can, and perhaps try to add ambience later.

Many times, the issue in smaller rooms is too much rather than too little reverberation. You might have omni's right on top of the players and yet it sounds like mush. Switch to directional mic's and things will clear up quite a bit.
Old 24th January 2013
  #5
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on the flip side, omnis can work quite well in a dead space, and in spaces that might be smallish but that still have a nice feel to them. there are, of course, plenty of rooms that are too ringy or too slapbacky or just sound not quite right for the music being performed, where you want to get rid of as much of the room sound as you can by using more directional mics. however, I have used omnis with very good results in moderate sized living rooms and small studios that have decent acoustic treatment - omnis have a nice open spacious feel to them that is hard to achieve with a cardioid mic, no matter how good a reverb you add to it later.
Old 24th January 2013
  #6
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Omnis always sound better than cards but in a poor acoustic they will have to be in close proximity to the source
8s are better directionals than cards too,they sound better. imho
Old 24th January 2013
  #7
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Quote:
Originally Posted by Rolo 46 View Post
Omnis always sound better than cards but in a poor acoustic they will have to be in close proximity to the source
8s are better directionals than cards too,they sound better. imho
Don't 8s pick up more room as well?
Old 24th January 2013
  #8
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Not with crafty angling and nulling
Old 24th January 2013
  #9
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Quote:
Originally Posted by Rolo 46 View Post
Not with crafty angling and nulling
In that case, I'd really like to how one could angle and null a pair of 8s to pick up as little room as a pair of cardioids. That might nudge me towards a pair of 8s instead of the KSM 141's which I'm about to buy .
Old 24th January 2013
  #10
Quote:
Originally Posted by polytope View Post
In that case, I'd really like to how one could angle and null a pair of 8s to pick up as little room as a pair of cardioids. That might nudge me towards a pair of 8s instead of the KSM 141's which I'm about to buy .
Think about how the 8 nulls all the way around its center axis.

When placing the mic, figure out the places where you are going to get the most wall reflection, the "bad room sound". Typically this is from the walls and floor/ceiling closest to the microphone. You can use this knowledge then to aim the null of the microphone to reject these reflections, and maximize source pickup.

Another good rule of thumb I've found is to aim the back side of your 8, the side away from the source, as much down the length of, or in the longest direction into, the room behind it. Beware of using an 8 with a wall right behind it! Phasing nightmares may occur!
Old 24th January 2013
  #11
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Quote:
Originally Posted by king2070lplaya View Post
Think about how the 8 nulls all the way around its center axis.

When placing the mic, figure out the places where you are going to get the most wall reflection, the "bad room sound". Typically this is from the walls and floor/ceiling closest to the microphone. You can use this knowledge then to aim the null of the microphone to reject these reflections, and maximize source pickup.

Another good rule of thumb I've found is to aim the back side of your 8, the side away from the source, as much down the length of, or in the longest direction into, the room behind it. Beware of using an 8 with a wall right behind it! Phasing nightmares may occur!
Thanks for the tips. I aware of making use of the nulls. But this kind of fiddling still require a certain level of cooperation from the room.
Old 24th January 2013
  #12
Quote:
Originally Posted by jnorman View Post
on the flip side, omnis can work quite well in a dead space, and in spaces that might be smallish but that still have a nice feel to them. there are, of course, plenty of rooms that are too ringy or too slapbacky or just sound not quite right for the music being performed, where you want to get of as much of the room sound as you can by using more directional mics. however, I have used omnis with very good results in moderate sized living rooms and small studios that have decent acoustic treatment - omnis have a nice open spacious feel to them that is hard to achieve with a cardioid mic, no matter how good a reverb you add to it later.

I agree completely. I love the sound of an omni in a dead room (sometimes i use one when recording vox in my control room) just to add some extra space.
Old 25th January 2013
  #13
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Quote:
Originally Posted by polytope View Post
Thanks for the tips. I aware of making use of the nulls. But this kind of fiddling still require a certain level of cooperation from the room.
It needs experiment
8's have a beam element, which is useful too
For too long I regarded directional mics as the acme
Experience revealed that the omni is the best
Followed by the 8.
Old 25th January 2013
  #14
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Quote:
Originally Posted by Rolo 46 View Post
It needs experiment
8's have a beam element, which is useful too
For too long I regarded directional mics as the acme
Experience revealed that the omni is the best
Followed by the 8.
What about hypercardioid?
Old 25th January 2013
  #15
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Has rear element too,never sounds as clean as an 8
Old 25th January 2013
  #16
Quote:
Originally Posted by Rolo 46 View Post
...Experience revealed that the omni is the best
Followed by the 8.
Who's "Experience"?

Sorry, but to post a statement like this reveals more about the poster than about the art and science of recording. To claim that one type of directional pattern is "best" is like saying one color shirt is "best" to a blind man. It's a blatantly flippant response and is simply not supportable by the real world experience of most of the world's successful audio engineers.

Quote:
Originally Posted by dgpretzel View Post
...In my (erroneous) thinking, I would tend to think that, when the reverberation is less than desired, I would want to get as much of the room as possible to capture what little exists. Hence, I would think that omnis would be preferred over cards, since the cards would reduce the effect of the room, thus reducing the reverberation that I might otherwise capture with the omnis...
It's not the amount of reverberation, it's the quality of the reverberant field. Some rooms have very uneven frequency dependent reflections and terrible standing waves. Those off-axis sounds can turn a recording into "mud", and must be eliminated to accurately record the musicians. Some rooms, a large church for example, may have decay periods that are simply too long to allow a good recording and would require the mics to be placed much too close to the sound source to achieve a correct direct to diffused sound ratio. More reverb is sometimes the last thing you need.

There are rooms and situations in which placement constraints clearly would result in a very poor recording if omnis or even Figure-8 mics were chosen instead of a more "focused" and limited-angle pattern. The range of "cardioid" mics available today provide vastly different off-axis frequency response characteristics which can be used to one's advantage in some situations.

Different rooms, different ensembles, different instruments all present their own challenges and have different optimal solutions. Many, many papers, articles and books have been published on the subject as well as endless discussions on this and other audio forums.

Omnis, Figure-8s, Hypo-cardioids, Cardioids, Hyper-cardioids, and even narrow-angle shotgun patterns all have their appropriate applications, just as moving coil dynamics, ribbons, and capacitor mic designs all have their appropriate place and use.

Properly positioned omnis in a good room are obviously an easy way to often get excellent, predictable results and are therefore used when appropriate. So are standard directional arrays using hypo-cardioid and cardioid mics. A good engineer considers many more factors than just the ratio of direct to reverberant sound in choosing the appropriate mics and their placement, and blanket "one size fits all" statements simply don't reflect the real world of on-location recording.

I routinely use spaced AB omni arrays, XY or ORTF arrays with outrigger omnis, "Decca Tree" like arrays, and sometimes spot mics. It depends on a long list of factors which include the ensemble configuration, the musicians, the room, the presence of an audience, the purpose of the recording, and many other considerations, and even with many decades of "experience" I'm still sometimes surprised by what work's and what does not.
Old 25th January 2013
  #17
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Bibster's Avatar
 

Quote:
Originally Posted by Lotus 7 View Post
Who's "Experience"?

Sorry, but to post a statement like this reveals more about the poster than about the art and science of recording.
Exactly, and had you taken the time to figure out who Rolo46 is, or what he's done, or who he worked with/for and the samples he has posted here on GS, you would've agreed with him.

Sorry, feeling a TF'ish-incident coming up.
Old 25th January 2013
  #18
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John Willett's Avatar
 

Quote:
Originally Posted by Rolo 46 View Post
It needs experiment
8's have a beam element, which is useful too
For too long I regarded directional mics as the acme
Experience revealed that the omni is the best
Followed by the 8.
Probably you find this because both of these are "pure" polar-patterns and everything else is a hybrid.

Omni is a pure pressure microphone and fig-8 is a pure pressure-gradient microphone.
Old 25th January 2013
  #19
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John Willett's Avatar
 

Quote:
Originally Posted by Lotus 7 View Post
Who's "Experience"?

Sorry, but to post a statement like this reveals more about the poster than about the art and science of recording. To claim that one type of directional pattern is "best" is like saying one color shirt is "best" to a blind man. It's a blatantly flippant response and is simply not supportable by the real world experience of most of the world's successful audio engineers.
Quote:
Originally Posted by Bibster View Post
Exactly, and had you taken the time to figure out who Rolo46 is, or what he's done, or who he worked with/for and the samples he has posted here on GS, you would've agreed with him.

Sorry, feeling a TF'ish-incident coming up.

Exactly - I am with Bibster on this one.

I don't always agree with Rolo, but I *do* know who he is and the very many years of experience he has.

And I certainly understand his thinking on this point and would have to agree with him for the reason I posted above.
Old 25th January 2013
  #20
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Quote:
Originally Posted by Lotus 7 View Post
Who's "Experience"?

Sorry, but to post a statement like this reveals more about the poster than about the art and science of recording. To claim that one type of directional pattern is "best" is like saying one color shirt is "best" to a blind man. It's a blatantly flippant response and is simply not supportable by the real world experience of most of the world's successful audio engineers.




I routinely use spaced AB omni arrays, XY or ORTF arrays with outrigger omnis, "Decca Tree" like arrays, and sometimes spot mics. It depends on a long list of factors which include the ensemble configuration, the musicians, the room, the presence of an audience, the purpose of the recording, and many other considerations, and even with many decades of "experience" I'm still sometimes surprised by what work's and what does not.
My experience dear chap,naturally
I was trained in the 60s, when ultra directional mics came into being
I thought the classic transducers out moded ,until a very experienced radio and film recordist demonstrated the joys of the omni to me ,but I still used the new guns,shotguns and hypercards with alacrity.
In the 70s electret omnis arrived,these proved very useful in many difficult situations, but I still went for the most directional arrays in my work ,mostly MKHs.
Radio mic placement was becoming the norm in TV,sometimes I was amazed at how good one omni could sound on the right voice, properly positioned.
Stereo TV drama and documentary had now arrived,MS technique came into my life,the figure of 8 was transformed from the studio ribbon beloved of radio, into a very pragmatic location device
The MKH 30 sounded very good,as did the 20, I started to use this more and more and when I retired and took up music recording ,as a self funding hobby, this with the 40 and 50 became my staple mics.
The cards were good,but the omni and the 8s were sensational imho.
I make no claim other than my own preference,I am not a world class audio engineer and I am continually surprised how simple arrays can sound so good.
I am a student of Audio history and know my Westrex and Blumlein,they really knew their stuff.
The omni and 8 were their staple.
I admire them.
Roger
Old 25th January 2013
  #21
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Given that I have about $1k to spend, should I get the ksm 141 or some fig 8 pair?
Old 25th January 2013
  #22
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SDC fig-8's hare horribly expensive. ksm141 is apparently a very good omni.
Fig-8 could be used more often than an omni, in case of less stellar room. But then the shure can transmogrify into a cardio, so...

@rolo46: Keep posting lengthy posts! ;-)
Old 25th January 2013
  #23
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Quote:
Originally Posted by Bibster View Post
SDC fig-8's hare horribly expensive. ksm141 is apparently a very good omni.
Fig-8 could be used more often than an omni, in case of less stellar room. But then the shure can transmogrify into a cardio, so...

@rolo46: Keep posting lengthy posts! ;-)
Horribly expensive as in $2K per mic? In that case, I have no choice then.
Old 25th January 2013
  #24
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Check out AEA r84
Old 25th January 2013
  #25
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mkh30 is ± $1200 IIRC...
Old 25th January 2013
  #26
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Quote:
Originally Posted by Bibster View Post
mkh30 is ± $1200 IIRC...
Hmm. At that price, I might want to get a couple of CMC5s first.

Anyway, I think I'm going to settle for a pair of KSM 141 for now.
Old 27th January 2013
  #27
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Thank you all.

I understand the gist of the many comments to be that "dryness" may not be preferred, but it is not the type of "badness" that one is trying to eliminate when using directioinal mics, as opposed to omnis.

Now it makes sense to me, when the pros advise eliminating the room as much as possible, when it is "bad".

I wonder if there may be some examples, someplace, that illustrate some of the various types of badness, with both omnis and directional mics.

Thank you for the many comments.

DG
Old 27th January 2013
  #28
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Quote:
Originally Posted by dgpretzel View Post
I wonder if there may be some examples, someplace, that illustrate some of the various types of badness, with both omnis and directional mics.

Thank you for the many comments.

DG
My living room sounds pretty bad. I tested my omnis there. Quite bad indeed.
Don't have the files anymore. I will try do do some samples once I've got my KSM 141.
Old 27th January 2013
  #29
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One can make ommis sounds as good as cardioids in a not stellar room by placing the mic closer to the source (may be not possible if the source consists in more than one instrument or voice) or by using baffles behind, besides or above the mic for attenuating the reverberation.

Here attached three piano takes recorded at home by means of Neumann mics: omni KM 133 D, wide cardioid KM 143 D, cardioid KM 184. The mic pair is in a small AB besides the end of the piano tail, same place for the three takes. There is a baffle behind the mics and another one above.
Attached Files

KM 184 (December 2012).mp3 (2.96 MB, 658 views)

KM 133 February2013.mp3 (2.83 MB, 637 views)

KM 143 January2013.mp3 (3.01 MB, 618 views)


Last edited by didier.brest; 26th February 2013 at 10:22 AM.. Reason: Old KM 133 and KM 143 takes replaced by mew ones.
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