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[Jørn Bonne]

Hi everybody!
Thanks for your enjoyable and informative posts on the PSW forums.

Can anybody help me with this:
I am trying to record solo acoustic guitar with M/S mic setup, using distances from 15 inches to about 2 feet. I get a wonderfully spacious sound, unlike anything I've gotten using other setups. One problem though:
The sound stage comes out lopsided, with the left much stronger than the right, whether I use software M/S matrix or mixer to set it up. I have also tried a stereo mic with built in M/S matrix. Again the sound got pulled to the left.
I am new to M/S recording, but this left/right offset seems to be inherent to using M/S in the nearfield. Am I right?
What's a good way to get the left and right rebalanced, without loosing width and mono-compatibility? Any experienced M/S nearfielders out there with some good advice?

Thank you

J

[Jørn Bonne]

Roland,

Thanks for your suggestions.

I'm using multipattern LDC's, M-mic set to card (omni gives me too much room sound in my particular room).

I have tried different angles and positions in relation to the guitar top. Guitar is a Lowden steelstring by the way. I'd like to stay within about 2 feet distance in order not to get too much room sound.

In all my tests the strong left/weak right thing has been a problem I can't seem to get rid off. It's led me to think that this is inherent in the M/S nearfield technique (L=M+S; R=M-S). I have not seen this mentioned in any M/S literature I've read, so I may be wrong in assuming this.

Thank you.

J

[jimmyjazz]

I hate to ask such an obvious question, but is it possible that you're placing the microphones in a location such that the signal coming from the "left" actually is hotter than the signal coming from the "right"?

There is no inherent bias to M/S.  If there were, it would be a mighty bad way to mic something in stereo.  I have always been able to achieve a realistic stereo image on, say, a drumkit when I mic it M/S from out front.  By "realistic", I mean that the snare drum comes out a bit right of center, and thus the right "channel" is louder when the drummer hits the snare.  Are you hearing the same thing -- is the main radiating part of the guitar a bit left of your mic array?

[guitarbth]

pardon my ignorance... but what exactly are you guys refering to when you say M/S? im just not familiar with that terminology. Thanks.

Brandon

[PP]

[Ruairi O'Flaherty]

For lots of mic techniques info go to http://www.dpamicrophones.com/ and follow th elink to the microphone university,

cheers,
Ruairi

[pipelineaudio]

I do this a LOT especially with 12 strings. Often I am even closer in than you mention. One side always comes out with a lot more bass and the VU meters get quite skewed to one side. Sometimes I will go in and adjust till they are more equal, but most often I find the most pleasing and most wide stereo field when they are where I like them and the bass is blasting way more on one side.

It sounds good, I deal with it. Pan the hi hat opposite or something

[sonixx]

M+S is much better in a more even and dispersed sound field... or balanced sound source.  Try balancing the mics around the body port.

If you're not stuck on using M+S, consider this technique...

Assume Right Handed Guitar Player

Mic Pattern: Start with Cardioid

Mic 1: Place mic about 18 to 24 inches in front, down a bit and to the left of the 15th fret... Pointed at the 12th to 15th fret

Mic 2: Placed over the guitar players right shoulder, pointed at the bridge and the same distance from the sound source as mic 1.  Move this mic some to balance the image.

Even if it's not right for this situation , give it a try.

-Keith-

[Steve G]

I don't think I read anywhere what patterns your mics are in.  If the side mic is not set to a figure-8 pattern it's going to sound unbalanced.  Steve

[sdevino]

The body of an accoustic generally generates a lot more SPL than the neck, So Left should be louder. You can decide whthter or not you want to adjust mic placement to balance vs keeping the sound you have with the way it is.

Steve

[Jørn Bonne]

pipelineaudio wrote on Fri, 01 October 2004 23:31]
I do this a LOT especially with 12 strings. Often I am even closer in than you mention. One side always comes out with a lot more bass and the VU meters get quite skewed to one side. Sometimes I will go in and adjust till they are more equal, but most often I find the most pleasing and most wide stereo field when they are where I like them and the bass is blasting way more on one side.


Aaron,

See you have had similar experiences with left/right offset using M/S in nearfield. When I try to make up for the imbalance by making the left and right more equal in volume the sound invariably gets narrower, thus loosing width and spaciousness.

Let me clear up a few things in response to some of the other replies:

Yes, my side mic is figure-of-eight.

I have tried to move the mic setup more towards the bridge (and beyond) of guitar to get more bass information to the right side of side mic. Still about the same offset in volume between left and right.

I notice on my mixer, where i have M-mic on ch. 1, S-mic on ch. 2 and phasereversed S-mic on ch.3, that M-mic playing by itself is centered with equal sound and meter action on both sides. Ch. 2 and 3 are also centered when played together, one panned hard left, the other hard right. But when I bring up M-mic with the S-mics, then the offset occurs. This leads me to think the problem is inherent in the M/S nearfield approach.

Keith, I like the micing approach you suggest and have been working with that as well. Still the M/S is my favorite, if I could just get it balanced.

Thanks all!

J

[jimmyjazz]

Quote:

I notice on my mixer, where i have M-mic on ch. 1, S-mic on ch. 2 and phasereversed S-mic on ch.3, that M-mic playing by itself is centered with equal sound and meter action on both sides. Ch. 2 and 3 are also centered when played together, one panned hard left, the other hard right. But when I bring up M-mic with the S-mics, then the offset occurs. This leads me to think the problem is inherent in the M/S nearfield approach.

There is nothing unusual in what you are describing.  Consider what happens when you listen to the 3 signals independently:  

* "M" is panned center, so L & R are equal.  
* "S" is panned hard left, so R is null.  
* "S-inverse" is panned hard right, so L is null.

However, "S" and "S-inverse" have the same signal content, save a phase inversion, so their RMS levels will be the same.  Pulling both faders up should show L and R being equal, even if the sound source is coming from (say) well off the left of the mic array.  It's only when you add in the "M" signal that you start to discern the directional nature of the recording.

M/S isn't X/Y.  You can't think of it that way.  (One can be converted to the other and vice versa, but that's another issue.)

[Fibes]

I think we are overlooking the fact that the closer you get the S to the signal of the M the more it will shift. Try placing the S signal more than 10db down from the M and listen, then bring it up in the mix, you hearing it? Of course you are. I'll let the mathematicians explain why this is the case with M/S recordings...

[jimmyjazz]

Fibes wrote on Mon, 04 October 2004 13:16

I think we are overlooking the fact that the closer you get the S to the signal of the M the more it will shift. Try placing the S signal more than 10db down from the M and listen, then bring it up in the mix, you hearing it? Of course you are. I'll let the mathematicians explain why this is the case with M/S recordings...

Bringing the "S" and "S-inverse" signals up relative to the "M" signal is equivalent to increasing the included angle between a pair of mics in X/Y.

[Jørn Bonne]

After reading the last posts I decided to do a test using a  stereo mic with built in M/S matrix. I should have done this a long time ago!

I recorded two testtracks with the same mic position. The first one, using the intended orientation of mic (left side of mic pointing towards tail of guitar) gave the expected strong left/weak right offset.
For the second I simply turned the mic upside down, the left side of mic now pointing towards the neck of guitar. And sure enough, it came out with a weak left/strong right offset.

My assumption, that M+S sum (L) inherently would be stronger than M-S difference (R) due to phasecancelation and more so in the nearfield, was proven wrong. Seeing, and hearing, is believing.

Now I'm back to work finetuning my mic-array positioning and, yes, I'm now getting the balanced sound stage I was looking for.

Really appreciate the help guys.

[George Massenburg]

Sorry it's taken me so long to post my own thoughts here.

I use M-S a lot.  I'll almost always use it as the main stereo pick-up on an acoustic grand, although I'll use one or two more mics to broaden/widen the sound.  And I'll use it on acoustic guitar.

One such use, Lyle Lovett's "Joshua Judges Ruth", got pretty good response, and a smattering of criticism.  I used an AKG C-24 with Stephen Paul 0.7u diaphrams oriented vertically.  I always print L-R (which makes it easier to deal with through a project) but almost always accentuate the "S" by 6dB or more, which gives me a really wide stereo space - if I want less "S", I pan the stereo in, same thing.  The criticism comes from the fact that Lyle sang everything live, and his voice is (depending on the tune and the intensity of the guitar) more or less always there in the guitar mic.  And (if one cares) the voice is much louder in one side than the other, and (again, if you care) since I'm hyping the difference between the channels, the "other" side is out-of-phase.

Yes, the sound stage is shifted by the effect.  Yes, the timbre of the voice is different left to right.  No, I don't think the problems outweigh the advantages.

George

[jimmyjazz]

I think Joshua Judges Ruth is probably the only Lyle Lovett record I don't own, but I'll rectify that problem today!  He is one of my all-time favorite songwriters and performers, even though he's an Aggie.  (It's TX/OU week, so my blood is truly running burnt orange these days.)

Regarding your post . . . could you clarify a bit?  It seems that you printed two-channel stereo (L & R), presumably the output of an M/S matrix, and you pushed the "S" such that the equivalent pair of X/Y cardioids had a very wide included angle.  Is that what you're saying?  If so, why was Lyle's voice off to one side?  Did you balance your mic array so the guitar was centered, leaving his vocals somewhat off center?

Also, I would love to hear what you think the advantages of M/S are over X/Y in the applications you mentioned (acoustic guitar, acoustic piano).  Are they primarily the mic choices you get to make -- say, the array you mentioned versus a pair of KM84s or some such?

Thanks for any thoughts you might have,

jim andrews
four/four records, LLC
austin, tx

[George Massenburg]

jimmyjazz wrote on Wed, 06 October 2004 10:25

[...] [Lyle]  is one of my all-time favorite songwriters and performers, even though he's an Aggie.[...]

You should get to know him.

Quote:

Regarding your post . . . could you clarify a bit?  It seems that you printed two-channel stereo (L & R), presumably the output of an M/S matrix, and you pushed the "S" such that the equivalent pair of X/Y cardioids had a very wide included angle.  Is that what you're saying?  If so, why was Lyle's voice off to one side?  Did you balance your mic array so the guitar was centered, leaving his vocals somewhat off center?

I turned knobs till it all - meaning the whole song - sounded right.  Don't know what specifically that meant.  Best to listen to it.

Quote:

Also, I would love to hear what you think the advantages of M/S are over X/Y in the applications you mentioned (acoustic guitar, acoustic piano).  Are they primarily the mic choices you get to make -- say, the array you mentioned versus a pair of KM84s or some such?

I did mention one thing, the ease of control of the stereo width.  The other important feature of M-S- is a single-point pickup (few if any spaced cardioids will sound the "same") which keeps both channels a lot more in phase.  For a piano in particular using spaced cardioids mean that notes caught in the trough of a comb filter are severely colored or lost.

GM

[jimmyjazz]

George Massenburg wrote on Thu, 07 October 2004 06:53

You should get to know him.

That's not likely to happen.  I did get to record his cellist John Hagen once, though.  That was fun.  He's obviously a classically trained musician, but he seems to like to push the envelope beyond "traditional" playing.

Quote:

I did mention one thing, the ease of control of the stereo width.  The other important feature of M-S- is a single-point pickup (few if any spaced cardioids will sound the "same") which keeps both channels a lot more in phase.  For a piano in particular using spaced cardioids mean that notes caught in the trough of a comb filter are severely colored or lost.

Thanks, George.  Just one quibble . . . I believe M/S and X/Y (not spaced cardioids) are "the same".  X/Y should maintain all the advantages (mono compatibility, no comb filtering) of M/S, but with different tonality due to the different microphones employed, right?  

I agree that spaced cardioids (something more akin to ORTF) have phase issues, although I must admit those haven't been too horrible in my experience.  (Other problems are probably dominating!)

Ever try true X/Y on an acoustic guitar or acoustic piano?

jim andrews
four/four records, LLC
austin, tx

[George Massenburg]

jimmyjazz wrote on Thu, 07 October 2004 10:03

George Massenburg wrote on Thu, 07 October 2004 06:53 You should get to know him. That's not likely to happen.  I did get to record his cellist John Hagen once, though.  That was fun.  He's obviously a classically trained musician, but he seems to like to push the envelope beyond "traditional" playing. Quote: I did mention one thing, the ease of control of the stereo width.  The other important feature of M-S- is a single-point pickup (few if any spaced cardioids will sound the "same") which keeps both channels a lot more in phase.  For a piano in particular using spaced cardioids mean that notes caught in the trough of a comb filter are severely colored or lost. Thanks, George.  Just one quibble . . . I believe M/S and X/Y (not spaced cardioids) are "the same".  X/Y should maintain all the advantages (mono compatibility, no comb filtering) of M/S, but with different tonality due to the different microphones employed, right?   I agree that spaced cardioids (something more akin to ORTF) have phase issues, although I must admit those haven't been too horrible in my experience.  (Other problems are probably dominating!) Ever try true X/Y on an acoustic guitar or acoustic piano? [...]

Sure.  All the time.  And recently, too.  I used crossed Sanken CU-44X's (capsule-to-capsule, pointing up and down with maybe 110 degrees between them) on Jon Randall's acoustic guitar for an entire disk.  Sounds fantastic.  Detailed, and warm at the same time.

The effect I'm sometimes looking for can be located somewhat more easily with an M-S source, although I'd agree that if you put crossed X-Y's through a matrix, and crank the "S" you'll widen the stereo spectrum (um, now that I think about it, the results shouldn't be as predictable as 90 degree M-S).  I haven't tried it, but probably should.  I really like my M-S mic, so there's no overwhelming motivation to do so.

George

[Jørn Bonne]

George,

Thanks for sharing some of your experiences with M/S recording. I'll check out the Lyle record.

The reason I am so set on getting a centered sound stage has to do with my special application. I'm recording songs with few sound components: vocal, stereo acoustic guitar and bits of percussion, looking for a big and spacious guitar sound, to take on the role of an orchestra behind the vocal, so to speak. Too much shift to either side would offset the balance of my minimalistic sound stage.

I tend to use less S-mic than you describe. My room leaves some to be desired and so does the off-axis response of my sidemic. I get a fuller, more substantial guitar sound with less S-mic. To make up I use a stereo widener with Blumlein shuffler to spread it out. This gives me the sound I'm looking for and I can adjust the width in the mix as needed.

J

[Rob Darling]

George,

I can see the instant advantage of a c-24 in m-s, with the capsules so precisely aligned, and with none of the hassles of multiple stands etc. that a dual-mic system presents.  Are there other less bank-blowing mics you've done this with?  Have you had success with using two mics in m/s, or do you consistently use dual-capsule mics?  

[Bill Mueller]

I recorded Micheal Hedges with a C-24, about ten inches from the guitar in X-Y with  about 100 degrees between the full cardiod capsules. I then used a pair of 414's in omni about three feet back and off to both sides. These were then surrounded front and back, by a four foot high stack of RPG diffusors. His albums were not necessarily "true stereo" however, because he also used his guitar pickup and lots of efx.

I have not used MS that much in the studio because I would just move the mic back or narrow or widen the capsules to adjust the amount of ambience. I think I will experiment a little. Thanks.

Best Regards,

Bill