Mic matching - Fact and Fancy

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Harvey Gerst

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I've seen this question posted here over and over:

"Do I need to used matched microphones for stereo recording?" or "Can I use two different microphones to record my acoustic guitar?". I thought it might be nice to clear the air and a few misconceptions at the same time.

"Stereo" is a very precise term, used to define the recording of something in spatial terms. Just because you use two mics to record something, it will come out "stereo". In many cases, you're just recording two different frequency ranges and separating them into left and right signals, but that's not stereo.

When you use two different mics (or two identical mics, for that matter) in close to record two different places on the same instrument, that is not stereo.

Stereo recordings require the use of two matched microphones, placed outside the near field, to create the illusion of the instrument in its natural environment. The placement can be coincident, near coincident, M/S, or A-B spacing to capture the acoustic space.

This use of matched mics and specific placement techniques is done to maintain the stereo integrity of the signal at all frequencies.

If you ain't doing that, you ain't really recording in "stereo". You can, for example, put one mic in close on an acoustic and position another mic a lot further back, but it ain't stereo. It may be flattering and it may sound great, bit it's not stereo in the strict sense of the word.

What you're doing is breaking the signal into two different ranges and recombining them in the mix to get a bigger, or fuller, or fatter sound, or whatever. But it's not stereo. It's a valid, but different technique.

If you want a two channel recording of your acoustic guitar, you can record with two different mics placed in whatever places sound best. If you want a true stereo recording of that instrument, you'll need two identical, closely matched mics, placed in the usual stereo recording placements.
 
Harvey Gerst said:
The placement can be coincident, near coincident, M/S, or A-B spacing to capture the acoustic space.

If you want a true stereo recording of that instrument, you'll need two identical, closely matched mics, placed in the usual stereo recording placements.
Click to expand...

Harvey,

Could you please explain the "usual stereo recording placements"? What exactly are "coincident, near coincident, M/S, or A-B spacing"?

Thanks

I'll be using a matched pair of MXL 603s
 
Re: Re: Mic matching - Fact and Fancy

VTgreen81 said:
Harvey,

Could you please explain the "usual stereo recording placements"? What exactly are "coincident, near coincident, M/S, or A-B spacing"?
Click to expand...
Coincident is just a fancy term for "damn close".

Near-coincident is just a fancy term for "not too damn close, but still pretty close".

M/S is a technique using a cardioid facing towards the source, while a figure 8 pattern mic is aimed sideways. The Figure 8 mic controls the width of the stereo field.

A-B is another way of miking, using a few widely spaced cardioids or omnis, used to capture extremely wide sound sources.

The "big thread" has diagrams of the various stereo miking techniques, as do most mic manufacturers' web sites, and a Google search on "stereo microphone techniques" will produce even more explanations.
 
Re: Re: Mic matching - Fact and Fancy

VTgreen81 said:
Harvey,

Could you please explain the "usual stereo recording placements"? What exactly are "coincident, near coincident, M/S, or A-B spacing"?

Thanks

I'll be using a matched pair of MXL 603s
Click to expand...
Read the big sticky thread at the top of this forum titled "How does diaphragm size/polar pattern relate to mic applications?"

It's ALL in there! :)
 
Thanks,

Hey Harvey, this is a little too freaky........

I'm listening to the Byrds greatest Hits, and just as I'm reading your post "It won't be wrong" starts.
Now is that some crazy coincidence or what?
 
Harvey Gerst said:
I've seen this question posted here over and over:

"Do I need to used matched microphones for stereo recording?" or "Can I use two different microphones to record my acoustic guitar?". I thought it might be nice to clear the air and a few misconceptions at the same time.

"Stereo" is a very precise term, used to define the recording of something in spatial terms. Just because you use two mics to record something, it will come out "stereo". In many cases, you're just recording two different frequency ranges and separating them into left and right signals, but that's not stereo.

When you use two different mics (or two identical mics, for that matter) in close to record two different places on the same instrument, that is not stereo.

Stereo recordings require the use of two matched microphones, placed outside the near field, to create the illusion of the instrument in its natural environment. The placement can be coincident, near coincident, M/S, or A-B spacing to capture the acoustic space.

This use of matched mics and specific placement techniques is done to maintain the stereo integrity of the signal at all frequencies.

If you ain't doing that, you ain't really recording in "stereo". You can, for example, put one mic in close on an acoustic and position another mic a lot further back, but it ain't stereo. It may be flattering and it may sound great, bit it's not stereo in the strict sense of the word.

What you're doing is breaking the signal into two different ranges and recombining them in the mix to get a bigger, or fuller, or fatter sound, or whatever. But it's not stereo. It's a valid, but different technique.

If you want a two channel recording of your acoustic guitar, you can record with two different mics placed in whatever places sound best. If you want a true stereo recording of that instrument, you'll need two identical, closely matched mics, placed in the usual stereo recording placements.
Click to expand...

Harvey, I have some of questions. And I'm certainly not trying to argue with you. I'm ignorant, and I admit it. :D I just want to understand where this recording definition of "stereo" came from and, more importantly, why it means what it does.

My non-musical understanding of stereo is that it means 3-dimensional. Many things can be stereo. For example, a stereo microscope produces images that appear 3-dimensional. A stereoscope, again, produces 3-dimensional images, and a stereograph "is" a 3-dimensional image.

My understanding is that music has three dimensions: (1) Front-Back=volume, (2) Up-Down=pitch (frequency), (3) Left-Right=panning. Ok, there's a fourth: time, but I'm not sure it's relevant to a stereo discussion.

With mono we have dimensions one and two. Stereo adds dimension three (left-right). So with this logic, stereo, in music, would simply mean panning (left-right) without regard to any other qualifiers, i.e. frequencies, loudness.

Now, I know the obvious "spatial terms" answer, as you stated, is it must create "the illusion of the instrument in its natural environment." That means, it must sound like it would to the two human ears in a given space (a qualification). I know the fore-mentioned "illusion" is what we are often trying to create: a true reproduction of what the human ears hear relative to the space and position of the sound source. But why does "spatial relativity to the human ears" have to be the only (and narrow) definition of stereo, when, in its purity, stereo simply means 3-dimensional?

For example, if I record an acoustic guitar in XY or ORTF with a matched pair and then pan the tracks hard left and right I will get a bigger than life image in the monitors, but it won't necessarily create the "illusion of the instrument in its natural environment." It will just sound bigger than life. Is this a true stereo recording/image? If not, how close would I have to pan them together before I achieved that "instrument in its natural environment" illusion?

Again, why does "spatial relativity to the human ears" have to be the only (and narrow) definition of stereo, when, in its purity, stereo simply means 3-dimensional (or maybe I misunderstood your definition). Also, what is the "natural environment" of a thundering distorted guitar blaring out of multiple Marshall stacks at a big rock concert? Is it even possible for that all-enveloping sound to be recorded in stereo? And if so, relative to what or whom?

I'm really not trying to be antagonistic, Harvey. I think these are legitimate questions and observations.

Yes, I've read the BIG thread, but I admit it's been awhile.

Thanks for your insights and explanations.
 
Re: Re: Mic matching - Fact and Fancy

tdukex said:
For example, if I record an acoustic guitar in XY or ORTF with a matched pair and then pan the tracks hard left and right I will get a bigger than life image in the monitors, but it won't necessarily create the "illusion of the instrument in its natural environment."
Click to expand...

Why wont it create the "illusion of the instrument in its natural environment."? That's the whole point of XY and ORTF micing. Have you tried it?

To a certain degree you are just muddying the waters. By most consumer standards stereo just means 'two track'. For recording engineers it is more specific to 'stereo imaging' during tracking.

To use your example of stereo 3D pictures - is it a stereo picture if you take two different pictures of the same source with different lenses then view one with each eye? No. You would have to take them with the same length of lense and have the lenses be about the same distance from each other as your eyes. Otherwise the 3d dimension, depth, is not properly represented.
 
<My understanding is that music has three dimensions: (1) Front-Back=volume, (2) Up-Down=pitch (frequency), (3) Left-Right=panning. Ok, there's a fourth: time, but I'm not sure it's relevant to a stereo discussion.>

Actually, the time is the most relevant to a 'true' stereo. Basically, signal reaches your left and right ears with little time difference. This difference creates this 'spacial' effect. With all the stereo mic techniques Harvey mentioned, plus binaural, Jecklin disk, and whatever else, we are simply trying to recreate our perception of the sound, its time delay between our years, and its direction. That is why it is so important for a 'true' stereo to get a closely matched pair... with one exeption: for MS recording you can use even different kinds of mics. For piano recordings I succesfully used SD as a Mid and LD as a Side, as well as LD as a Mid and ribbon as a Side. Of course, the mics should be placed as close to each other as it is possible, otherwise... it is not MS anymore.
All stereo techniques have their own pros and cons, and the judgement can be done only for given particular situation.

Use your ears, Gentlemen, use your ears...
 
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Re: Re: Re: Mic matching - Fact and Fancy

TexRoadkill said:
Why wont it create the "illusion of the instrument in its natural environment."? That's the whole point of XY and ORTF micing. Have you tried it?

To a certain degree you are just muddying the waters. By most consumer standards stereo just means 'two track'. For recording engineers it is more specific to 'stereo imaging' during tracking.

To use your example of stereo 3D pictures - is it a stereo picture if you take two different pictures of the same source with different lenses then view one with each eye? No. You would have to take them with the same length of lense and have the lenses be about the same distance from each other as your eyes. Otherwise the 3d dimension, depth, is not properly represented.
Click to expand...

Of course I've tried it. Have you? It sounds like a really big guitar--not like an acoustic truely sounds when you are sitting out in front of it. The image is "bigger than life," not natural.

And your rant about "stereo pictures" is what I call muddying the waters. I referred to real-world examples of things that are considered by science to be 3-dimensional, or stereo as their names imply, in order to substantiate my definition of stereo. That's all. If you want to argue if those items are stereo or not, go argue with the scientists (or whoever) named them. :D If you want to argue what a "stereo picture" is or is not, maybe you should go visit some Photography forum. While you're away, go look up the definition of "stereo" in a good dictionary.

In the meantime, I'll wait for Harvey to further explain the meaning of audio "stereo" from his viewpoint, if he wishes. Because that's who I asked. I wasn't looking for a confrontation, just some civil, more indepth explanations. You provided neither.
 
<In the meantime, I'll wait for Harvey to further explain the meaning of audio "stereo" from his viewpoint, if he wishes. Because that's who I asked.>

Hm,

Does it mean I did not have to bother taking time to answer?
 
Marik said:
<My understanding is that music has three dimensions: (1) Front-Back=volume, (2) Up-Down=pitch (frequency), (3) Left-Right=panning. Ok, there's a fourth: time, but I'm not sure it's relevant to a stereo discussion.>

Actually, the time is the most relevant to a 'true' stereo. Basically, signal reaches your left and right ears with little time difference. This difference creates this 'spacial' effect. With all the stereo mic techniques Harvey mentioned, plus binaural, Jecklin disk, and whatever else, we are simply trying to recreate our perception of the sound, its time delay between our years, and its direction. That is why it is so important for a 'true' stereo to get a closely matched pair... with one exeption: for MS recording you can use even different kinds of mics. For piano recordings I succesfully used SD as a Mid and LD as a Side, as well as LD as a Mid and ribbon as a Side. Of course, the mics should be placed as close to each other as it is possible, otherwise... it is not MS anymore.
All stereo techniques have their own pros and cons, and the judgement can be done only for given particular situation.

Use your ears, Gentlemen, use your ears...
Click to expand...

Thanks for the reply, Marik. You aren't Harvey, but you are knowledgeable and a gentleman. I do understand your explanation of the importance of "time" in the spatial image, and I am familiar with and have used most stereo micing techniques, including MS. Perhaps I'm splitting hairs, here. I guess I'm just trying to reconcile the classic meaning of stereo (3-dimensional) with the seemingly more restrictive recording definition: it must sound natural. Again I ask, what is natural about a person standing in the middle of a big stadium listening to a rock guitar screaming through speakers stacks that are hundreds of feet apart?
 
Tdukex- What about my reply didn't you understand? Obviously you do not undestand how stereo photography works either. If you think an XY mic of a guitar sounds 'bigger then life' you might just need to turn it down.

I tried to give you a rational and thought out explanation that even you could understand but apparently I failed. I guess we can wait for Harvey to tell you the same thing.
 
Whoa, let's not get too steamed up about the subject. First, tdukex has some legitimate questions, and marik and TexRoadkill provided some great answers, but it's a subject that requires further discussion.

You can place a lot of mono recorded instruments in various "panned" positions and many will call that a"stereo" recording, but not by the strict definition of the term stereo, and maybe some background on the term and recording techniques are in order at this point.

With the introduction of two channel recorders in the late 50's and early 60's (and the appearance of stereo FM radio), classical recording engineers saw this as a unique opportunity to finally recreate the "concert hall experience" in the home, and the real boom in the sale of high fidelity equipment started.

Various techniques were tried, discarded, or become standards for different countries. Remember, most of these recordings had to be mono compatible and able to be broadcast over traditional radio station equipment.

The two categories of stereo recording could be separated into two camps: binaural (headphones only), using a dummy head, with mics for "ears", and stereo (into two speakers, using any one of a 1/2 dozen different stereo recording techniques).

Binaural was doomed from the start because only a few people at a time could listen to the recordings, and really good headphones were very expensive. That left stereo and the discussions (arguments, really) started at once. How could you fit a symphony orchestra into the average living room?

The answer is of course, you can't, so the obvious solution was to transport the listener to the concert hall, by judicious stereo mic placement - and reasonable playback levels. To a large degree, that technique worked fine for years. At least, it did until multitrack recorders came along and opened up whole new possibilities for audio manipulation.

For popular music, the idea of true stereo recordings has pretty well died, but it's alive for the most part in classical music, and that's where the acoustic guitar recording might serve as a good example.

tdukex is right about the mega-groups and rock music in general - an artificial "stereo image", created in the studio is the norm these days. And the sound is exciting when played back thru a stereo system, or a 5.1 surround sound system.

But for an "accurate" "illusion" of an acoustic guitar, played as if the performer were in the room with you, true stereo recording techniques, using matched mics and correct positioning are the best chances for realism.

Now, for "something else", in the way of a guitar recording (played over two speakers), your guess is as good as mine. Anything is valid if it sounds good, but don't confuse that with "real stereo". It's not the same thing. That doesn't mean it's bad if it ain't stereo; it's just "something else".
 
Harvey, thanks for the detailed reply. Now we're getting somewhere. You are correct, there is no reason to get all steamed up over a discussion of stereo.

I think, in a round-about way, you answered my acoustic guitar question.

You said, "But for an "accurate" "illusion" of an acoustic guitar, played as if the performer were in the room with you, true stereo recording techniques, using matched mics and correct positioning are the best chances for realism.

"Now, for "something else", in the way of a guitar recording (played over two speakers), your guess is as good as mine. Anything is valid if it sounds good, but don't confuse that with "real stereo". It's not the same thing. That doesn't mean it's bad if it ain't stereo; it's just "something else."

So, by your definition of stereo being "accurate" and "realistic," I extrapolate from this that if a "true stereo recording" of an acoustic guitar is panned so hard left and right that it produces a "bigger than life" guitar sound, the playback is not an accurate representation of the "source in space" and is therefore not true stereo. The recording was recorded in true stereo, but the end product that is played back cannot be true stereo because it is neither accurate nor realistic. Is that a fair conclusion?

Also, I think you answered my rock guitar question when you said, "For popular music, the idea of true stereo recordings has pretty well died...(and for) the mega-groups and rock music in general - an artificial "stereo image", created in the studio is the norm these days." According to your definition of stereo, this makes absolute sense to me.

Thanks again for the reply.
 
Most of what is passed off as stereo today is what I call "panned mono". I love the sound of true stereo recordings, being very fond of M-S technique. In practice though, I find as others do that the popular music soundscape becomes crowded very fast, and that often it's the duller sounding mono track that sits better in the mix. But I use stereo miking techniques when I can, which is pretty often
I'm not entirely sure that I agree that a non matched pair of mics doesn't yield a stereo recording though. This may be a matter of semantics, and I certainly yield to Mr. Gerst's respectable knowledge and experience, but in my own humble opinion, the essential element of stereo is the capture of time/level differences that the ear and brain use to cue location. In the real world, rooms are seldom acoustically symmetrical, and very often, neither are our ears. Even a wildly mismatched pair of microphones will provide the essential elements of aural location. It may be inaccurate stereo, but it is, I submit, stereo.

Respectfully, RD
 
Yes, it is stereo, but I did say, "But, for an "accurate" "illusion" of an acoustic guitar, played as if the performer were in the room with you, true stereo recording techniques, using matched mics and correct positioning are the best chances for realism."

Using less than matched mics will result in the possibility of the stereo image wandering, or shifting dramatically, due to frequency variations between the mics. I didn't even say that matched mics work perfectly, just that they "are the best chances for realism."

But yes, it would still be stereo.
 
hi, I am being the 3rd cousin of big time engineer jack ortman. Can i be recording in stereo with professional accuracy with oktava 219 microphones? Please tell me all you can be telling me about these microphones. Are they being good only sometimes are all the times for super accurate professional fidelity stereo sound?
 
sweetnubs said:
hi, I am being the 3rd cousin of big time engineer jack ortman. Can i be recording in stereo with professional accuracy with oktava 219 microphones? Please tell me all you can be telling me about these microphones. Are they being good only sometimes are all the times for super accurate professional fidelity stereo sound?
Click to expand...
You're related to Jack Ortman? THE Jack Ortman? Jack Ortman is possibly the finest recording engineer on the planet, so if anything I've said ever contradicts his advice, I would seriously suggest you forget anything I've said and go with his suggestions.

Even Fletcher won't argue with Jack Ortman's advice.
 
Harvey, were you around when they were doing the 3 speaker setups? As I recall the early stereo engineers felt that was the best way to represent a realistic image. If so did you notice that being more realistic having a true center speaker?

I'd like to play around with dual M/S setups and a surround encoder when I get the chance. It would be cool to record a groupl of musicians with two M/S setups back to back and the group around the mics. Then run it back through a 5.1 system. It might be a great way to capture classical and bluegrass.
 
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