Topic: Recording a matrix using Cards & Omnis....opinions?

[ideal77dlr]

I'm recording an open air show soon....undercover style....not a problem, but I was thinking about doing something different and using A-B close to the stack on my cards and also running another recording into my other recorder using Omnis and then merging them together in post.

Has anyone done this? Is it worth doing? I've got good results just using my cards but wondered if running the Omnis at the same time, perhaps with a different configuration might give me something extra.

Any thoughts?

[fandelive]

Well, I'd rather bring a friend of mine to the show and tape from two different spots (lets say left stack and right stack, or front or stack and sweet spot) than do two tapes from the very same spot.

Considering your rigs, I'd run omnis from the front or stack and cards from sweet spot.

[page]

Well, I'd rather bring a friend of mine to the show and tape from two different spots (lets say left stack and right stack, or front or stack and sweet spot) than do two tapes from the very same spot.

Considering your rigs, I'd run omnis from the front or stack and cards from sweet spot.

I concur with all of this.

[acidjack]

^^ Agree, if this is an option.

But in general, yes, I think combining two sets of mics can be very useful, especially if you are not in an optimal location.  For example, recently I was in a venue where I have to run on the balcony, and all center spots were gone.  So I set up my mk41s fairly close to the stack (15ft or so) on a clamp/extension arm, but that can sound weird because the mics are so directional.  I threw some 4061s out on the extension arm as well.  Filled out the sound nicely and gave a good option of how much direct vs. reverberant sound to mix in.  Same principle applies with the small mics.  Also with any cards that small, some omnis will add some much-needed additional bass. 

[fandelive]

Also with any cards that small, some omnis will add some much-needed additional bass.

In some (major) cases, I found out omnis to add much more boomy room reverb' than actual music bass. That's why I switched to cards.
I deal with placement to get the right amount of bass.

ideal77dlr, you might want to try the 'two spaced taping spots' thing with two pair of cardioid mics. The matrix would certainly add the needed amount of bass too.

What acidjack suggests is worth a try too, especially if you're alone.

There are plenty of solutions actually. It's a matter of sound taste

[DSatz]

> Same principle applies with the small mics.  Also with any cards that small, some omnis will add some much-needed additional bass.

Acidjack, please pardon me but if I read you correctly, you seem to believe that the bass response of a microphone depends on its size. With the way certain beliefs get ingrained I doubt whether I can influence anyone's thinking about them--but I'd like to try to spell out some of the basic physics that explains why this one is false.

Devices that produce sound in various frequency ranges and pump it out into rooms have to be somewhat matched to the sound wavelengths in order to be efficient. That's why basses and 'cellos are larger than violins, and all other things being equal, a large loudspeaker with a range that goes down to frequency X will be more efficient than a smaller loudspeaker that has a range down to the same frequency X.

With devices that receive sound, like microphones or our ears, sensitivity becomes the issue. There are multiple, interacting factors just as in loudspeakers or acoustic musical instruments, but for sound-receiving devices the diaphragm size isn't the controlling factor for low-frequency response. Instead, it becomes the controlling factor for high-frequency response, in that the diaphragm becomes an obstruction and causes shadowing. The larger the diaphragm, the wider the range of frequencies (from the top downward) which will be affected. But if the sound-producing device can propel the sound energy to the place where it's being received, a diaphragm of any given size can pick it up. If that weren't true, we wouldn't be able to hear low frequencies with the rather small eardrums that we have. And the measurement microphones that acousticians use typically have flat frequency response to well below the audible range, such as to 2 Hz or thereabouts, even in the 1/4" versions.

So those are the basic facts. If I try to explain why some people think that "everybody knows" that large-diaphragm microphones have more/better bass than small-diaphragm microphones, I'd have to speculate and it would get a little complicated--basically I think it comes down to the low-frequency pattern spread of dual-diaphragm cardioids and proximity effect, both of which produce very real, audible effects that engineers utilize all the time. But they're not the same as the low-frequency response (or range) of the microphone when you compare apples to apples.

If this whole rant was off-base, my apologies; I do that sometimes.

--best regards

[acidjack]

I don't doubt that the science of what you are saying is absolutely correct.  My point was perhaps less a scientific one than an anecdotal one; that is, I am not aware of any small (and by "small", I mean, really, smaller than a standard size small diaphragm condenser like a Schoeps Mk4) cardiod microphone (or certainly anything more directional) that produces what I view as sufficient or realistic bass response.  On the contrary, I think many very small, even tiny omnidirectional mics (DPA 406x, Countryman B3, any of the little Church Audio mics) do that just fine.  And in the specs of all of the very small directional microphones I'm aware of, I think that anecdotal view is borne out - but you would know better than I.  I know for instance that DPA makes some very high-end very small instrument mics (the 4081 being the new one), and even these have fairly significant roll off on the low end compared to, again, a typical-size SDC.

I would be overstepping the bounds of my limited knowledge to say it's impossible to make a tiny cardiod microphone that can reproduce the bass response of a standard-sized SDC; I am just not aware of anyone who has done it.

> Same principle applies with the small mics.  Also with any cards that small, some omnis will add some much-needed additional bass.

Acidjack, please pardon me but if I read you correctly, you seem to believe that the bass response of a microphone depends on its size. With the way certain beliefs get ingrained I doubt whether I can influence anyone's thinking about them--but I'd like to try to spell out some of the basic physics that explains why this one is false.

Devices that produce sound in various frequency ranges and pump it out into rooms have to be somewhat matched to the sound wavelengths in order to be efficient. That's why basses and 'cellos are larger than violins, and all other things being equal, a large loudspeaker with a range that goes down to frequency X will be more efficient than a smaller loudspeaker that has a range down to the same frequency X.

With devices that receive sound and turn it into other forms of energy, like microphones or our ears, the concern for efficient coupling into the air of a room becomes the inverse of what it is for sound-producing devices--sensitivity becomes the issue. Sensitivity measured across a range of frequencies is called frequency response. There are multiple, interacting factors just as in loudspeakers or acoustic musical instruments, but for sound-receiving devices the diaphragm size just isn't the controlling factor for low-frequency response. Instead, it actually becomes the controlling factor for high-frequency response, in that the diaphragm becomes an obstruction to sound and causes shadowing effects. The larger the diaphragm, the wider the range of frequencies (from the top of the range downward) will be affected by this.

If the sound-producing device can propel the sound energy to the place where it's being received, a diaphragm of any given size can pick it up. If that weren't true, we couldn't hear low frequencies with the rather small eardrums that we have. And the measurement microphones that acousticians use typically have flat frequency response to well below the audible range, such as to 2 Hz or thereabouts, even in the 1/4" versions.

So those are the basic facts. If I try to explain why some people think that "everybody knows" that large-diaphragm microphones have more/better bass than small-diaphragm microphones, I'd have to speculate and it would get a little complicated--basically I think it comes down to the low-frequency pattern spread of dual-diaphragm cardioids and proximity effect, both of which produce very real, audible effects that engineers utilize all the time. But they're not the same as the low-frequency response (or range) of the microphone when you compare apples to apples.

If this whole rant was off-base, my apologies; I do that sometimes.

--best regards

[DSatz]

(sigh) This is why I prefaced my message as I did, and why I hesitated to say anything at all. I'm well aware that "large-diaphragm microphones have more/better bass response" is a belief that people will strive to maintain no matter what anyone else says--and I mean "maintain" as a very definite activity of the mind.

Of course there are particular microphone comparisons that could lead a person to that conclusion. But in order to judge whether a set of examples can "prove" a rule or not (and exactly what they prove if so) you have to choose your theory first. As a result, almost every experience can seem to confirm the theory or belief that one already has. In this case the belief is maintained despite many, many such exceptions, yet many people cannot even imagine how it could possibly NOT be true. Lower frequencies = longer sound wavelengths, ergo bigger must be better at capturing low frequencies.

I had to finish writing my earlier message in a hurry, despite its excessive length. As soon as I shut off my computer, I thought of a convincing metaphor that I could have used. Try this on, please: Imagine a cove at the seacoast. The tide is coming in, so the overall level of the water is rising gradually, almost unnoticeably. At the same time, gentle, regular waves are rolling in. Finally, imagine a group of little ducklings floating in the water; they bob up and down in the waves, and their average level rises (too slowly to notice as such) with the incoming tide.

If you can imagine that scenario, and if it makes sense to you that the ducklings would remain floating on the surface of the water, then that's really all it takes. Thank you! Because if you believe that only large objects can respond to large waves, then logically you must expect the ducklings to keep a roughly constant altitude (relative to the floor of the cove) despite the waves and the tide, because they are so small. You would have to imagine them being submerged by each incoming wave, and probably drowning as the tide comes in. If that absurd (and tragic) outcome seems logical to you, then by all means please go on believing as you do about large diaphragms and low-frequency response, because that's the exact analog.

On the other hand if you're the Greek god Poseidon and it's your job to generate huge waves, you'll need substantial power, and for that function it helps greatly to have a big surface area with which to push and pull. But once the wave exists even a tiny object can respond to it perfectly well. With the small mass that the ducklings (or your eardrums, or the diaphragms of microphones) have, they don't need to absorb the entire energy of the wave in order to be moved.

--best regards

[Cheesecadet]

I typically run a pair of cards DIN and a set of 4061s spaced at 66cm on a homemade mount I made (on the same stand) at almost every show I attend.  I don't always mix the sources, however, I am always very pleased when I do. 

If I had more time I would probably mix the sources every time as I can control how much of each mic makes it into the final mix based on what I think sounds best.

[Will_S]

Not sure where you draw the line for supertiny, but I've always thought the AT822 offers fairly solid bass, certainly more substantial than say At853 or Sennheiser MKE40.  Once you strip away the mesh and foam, its capsules are about the same size as lavalier cards too.

[DSatz]

mshilarious, I definitely see what you mean, and I've modified what I wrote above, hoping to avoid or possibly undo a potential insult. And that's not just on some general principle of being nice; it's because you seem to be a careful thinker, and I really value that.

I don't know many of the mikes being used as examples here (though I have seen an AT822 with its cover off; it has small-diaphragm capsules) so I'm going to keep this general and then back off some. Designers of microphone capsules have numerous variables to work with, and they're usually trying to optimize the result for a particular application or to cover a particular group or range of applications. Most directional microphones aren't designed to have flat frequency response to the lowest possible frequency, since to do so to any significant extent would require an increase in damping which would in turn reduce the sensitivity and the signal-to-noise ratio.

But more to the point, completely apart from the technical difficulty of making a really good-sounding supercardioid, most users have little use for truly deep low-frequency response in directional microphones, and it could even harm sales. Generally those mikes are sold for "better clarity" and with more highly directive microphones such as supercardioids and hypercardioids, the design goal is speech pickup in rooms where noise and excessive reverberance at low frequencies is a problem. In other words, the very competent engineers at A-T (and for that matter Neumann) are probably proud that they avoided having too much deep bass in the supercardioids that were mentioned.

Of the millions of microphones manufactured in the world, only a small percentage are sold to people who really want the maximum possible sonic transparency. As a WAG I'd say that no more than 3 - 5% of the microphones in the world are used for music recording by people who care enough about the result to get involved the way people here are--and even most of the people here don't seem to want maximum sonic transparency as such; instead they want the impossible: microphones and other equipment that will produce good-sounding recordings when the original sound quality of the live event wasn't really all that good. Unfortunately, most live musical events just aren't that well arranged for effective recording by simple means.

All this has a big effect on what most manufacturers aim to produce. Particularly in the popularly-priced part of the market, what you see is the result of microphone design engineers trying to produce a product that will catch on and sell as widely and profitably as possible. It isn't (generally) that they're aiming to produce the deepest possible bass, the cleanest, most consistent polar pattern across the frequency range, or a high-frequency response that's free of audible peaks and bumps. Market forces don't and won't bring that about for the most part.

So it should never be assumed that the characteristics of any given microphone represent the manufacturer's attempt to reach the ultimate in sound quality that is physically available, even for the given price.

--best regards

[Gutbucket]

I assumed the primary factor is simply that the market for very small directional mics designed specifically for stereo recording at a significant distance from the source is insignificant and not worth chasing for larger mic manufacturers.

Beyond the physically imposed lower end roll-off of any directional mic that has some degree of figure-8 response to it (in the low bass range rather than midbass and unavoidable AFAIK without corrective EQ like Sennhiser does with some of their designs), I just assume manufacturers design and build very small directional mics specifically for use up close where a tailored response is advantageous.  I'm thinking of things like balancing proximity response, reducing handling noise, and a contoured response that might work better than a flat response for reinforcement work (vs studio recording). 

What I hoped would be an exception to that are very small directional mics targeted specifically as hanging choir mics, an application which seems closest to the way many of us use the mics – primarily in that they are used at a greater distance.  Like Jon, I've noticed what seems to me odd specifications for mics marketed for that particular application.   For instance, although the DPA 4098H hanging choir mic does have a greater sensitivity than the otherwise similar 4099 and 4081 which are designed for close-mic’ing, the response chart indicates an identical response: bass flat down to 40Hz at 20cm, but rolled off starting from ~600Hz farther away, looks to be about -3dB at ~250Hz and around -8dB at ~80Hz at 1meter (the farthest measurement indicated).

One meter is closer than a choir mic would be used in its intended application. That has me scratching my head a bit.  I assume the answer is partly that although the 4098H is marketed as a choir mic and may work well for that application, the design was made originally for close mic’ing (4099, 4080 @ ~20cm) and adjusting sensitivity is simple compared to redesigning the housing for a flatter mid bass response at distances more typical of the intended application.  I assume the other part of the answer has to do with microphone measuring convention not matching well with intended use.  Other very small directional mics marketed specifically as hanging choir mics in a similar price range which I'm aware of (thinking of those from AT & Audix) seem to have a similar attenuated midbass and lower response.  Similar carry over of close/lavalier oriented designs I'd guess? The more costly, slightly larger compact directional microphones from Schoeps, Neumann, Sennheiser, DPA that are not originally designed for lav type use and do not have that respose are presumably superior used in hanging choir mic applications.

I like the duckling analogy.
If it acts like a duck and floats like a duck..

[Massive Dynamic]

Unless I obscure the backplate and turn it into a subcardioid, but that's cheating . . .

mmmm...Naiant subcards...

[Gutbucket]

It doesn't have to be for stereo recording; I think the choir mic market is exactly where it would be useful, and that market is not small.

Precisely my motivation for keeping an eye on those to potentially repurpose for the type of recording discussed around here.

PS  Why aren't subcards "hypocardioid"?  Other than the obvious reason   Or even better, "ovoid"?  I am totally going with ovoid

I have seen reference to hypocardioid in microphone literature.  I've also wonderd why the confusing mix of Greek and Latin prefix terms.  Why not just stick with Greek modifiers for the Greek term cardioid?

hypo/hyper - Greek
sub/super - Latin

Seems the Latin alternatives should be:
subcordis/ supercordis

But there is a strong tradition of mixing Latin and Greek terms in language in general and audio in particular, even within one compound word.  How about this bastard etymological audio love child:

Quadraphonic

Shouldn't that have been either quadrasonic, or tetraphonic?

Eitherway, I'm totally with you on ovoid! 

One day I was mathematically screwing around with polar patterns and I made a cloverleaf.  Utterly useless as far as I can tell, and practically probably it wouldn't work as the constituent patterns of real-life capsules aren't really that tight, but it did look cool . . .

Getting all Ambisonic with 2nd order patterns!





AFAIK, real world microphone patterns beyond 1st order can only be practically derived using beam forming techniques and complex matrixing of large numbers of omnis.

Sweetbreads and cottage-loafs..

[T-90]

I like the duckling analogy.
If it acts like a duck and floats like a duck..

ha!  i just finished reading this thread and about 3/4 of the way through page 1 i wondered to myself, why has gutbucket not chimed in on this one....then on over to page 2 and here you are, right where you should be.

great thread btw fellas.