Mid Side technique question

[stuntbutt]

Just realized that info is for the "Roswelite" version, not the standard Naked Eye.

[geeek]

Maybe... but the same thing happens with my neumann valve mic, which, when in fig 8, it should in theory be the same response from both front and rear.

The conclusion I have drawn is that the front of the fig 8 mic, which is the Left Side channel gets more guitar body than the Right Side (rear of fig 8).

Frequency detail is obviously much stronger on this side, and therefore, when added to the Mid mic, it's amplifying those frequences that the mid mic is, at the same time.

It's annoying!

I dunno what to do.. do you guys think the sound is bad from listening to the samples?

Cheers

[geeek]

Originally Posted by stuntbutt

Just realized that info is for the "Roswelite" version, not the standard Naked Eye.

no no, it's the naked eye too.. mine is like that

nice mic for the price really

[Corran]

Personally I don't think you should worry about people listening to it in mono...that's not very likely these days.

Sounds very good to me with the adjustment in volume.

[Crowley]

When I listen to these with headphones, it sounds to me to be reasonably centered, coherent, and realistic.

When listened to through the monitors, it does seem shifted to me also. In mono I think I hear cancellation in both headphones and on the monitors. I cannot guess if there a phase error somewhere, but it seems possible.

Although Naked Eye is not generally recommended for M-S, it can be used for it as long as the tonal differences on each side are not bothersome to you, as one side is significantly brighter. Other than that, the two lobes are still 180 degrees apart and of nearly equal amplitude. I have actually listened to them in Blumlein but not in M-S configuration. Wes Dooley's site once had a lot of info on M-S that I think is still there and probably worth looking at.

The audio specs on Naked Eye Classic and Naked Eye Roswellite are very, very close, the only big difference being the ribbon material, and the body color. They are both intentionally very asymmetric.

Bob

Latest News from Crowley and Tripp's Lab

[geeek]

soooo.. what do you generally think about the sound?

good enough as the uniform ac gtr sound throughout the album?

thanks in advance

[John Willett]

Originally Posted by mohthom

To ensure that your matrixing is correct;

Turn off the centre channel. Remove the left/right panning (pan both dead centre). Do not adjust the phase flip. The sounds should cancel.

It's that simple!

MohThoM

Yes - this is vital.

The original and polarity-reversed versions of the fig-8 *must* be absolutelt identical il *all* respects and this is the best way of making sure all is OK.

If you can hear anything at all when you do this test, something is wrong.

[Crowley]

Yes gain equal and 180 degrees apart will cancel. I just did it with a NE no problem. Had I thought it through I would have realized this was OK even with some asymmetry of pattern as all we are doing is splitting, inverting one, and then adding otherwise identical signals to demonstrate cancellation. Completely goes away.

That works with any signal, but with a fig 8 of course you have spatial info in there that works with the center mic.

What you had sounded fine to me through headphones, and my normal listening environment here on my "good" system at home.

Bob

[geeek]

Thanks Bob,

do you think it sounds wrong/bad? I'm not sure I hear this canellation..

I'm worried now, because this is gonna be the guitar sound for the whole album.. Should I start fresh?

I wanna get more work afterwards! I'm young, passionate and have loads of ideas..

I just don't want my first commercial work to go down like a lead balloon.

Eeek!

[Crowley]

I think it sounds fine. I say keep it unless you know your product will get primarily used in a mono channel, which is where besides a ring tone?

The guitar is not exactly in the null of the figure 8. It has width and the two lobes of the figure 8 may be adding/subtracting as a function of position. The body is to one side of the neck. To me, that sounds realistic and natural, not overly widened or otherwise messed with.

The room ought to be a factor as well, as much of the info coming in on the two fig 8 lobes may be reflections/ambient, though it does not seem that way here.

Latest News from Crowley and Tripp's Lab: Fostex Mid Side Stereo Mic

Here is a shot of one of the old Fostex M-S mics, not really ribbon mics, but a type of flat dynamic that was very cool looking inside. Anyway the point is how the fig 8 mic relative to the cardioid, FWIW, at 90 degrees. The cardioid mic is pointed right into the null of the fig 8. Since the fig 8 null has an angle, the width will be greater with more distance. I am interested in hearing from those who have used M-S in close-up situations, such as near an instrument with obvious L-R width, such as acoustic, as I have considered making an M-S mic. Very close and I think selected portions of the instrument itself become apparent at specific locations in the sound field.

I looked at the Wes Dooley site and I see the paper from AES referenced, but not available there as a download. Chances are he would send it to you if you asked him.



Bob

[geeek]

That's good to hear Bob.

I think it sound quite natural too, obviously it would be weighted tot he side slightly, I shouldn't worry too much.

I also prefer the ribbon sound over the valve one for this guitar.

I think I'd like to read that paper you mentioned, do you think if I contacted him he'd send it?

I feel I'm at a good stage to take all this in. I've never been so enthusiastic about technique since I started working on this project with real gear

btw.. are you Bob Crowley? Did you design my microphone?

If so.. It's fantastic.. I really love using it

[Crowley]

To reassure you:I just played back on the good system, both channels into one monitor, and it sounds fine here but obviously lacks spatial info which brings a lot to this solo recording of acoustic guitar. Two monitors in mono sound the same. The stereo offset that you are worried about is not very big and you could simply adjust the gain in one channel slightly if it bothers you. The cancellation that I am referring to is a "possible" cause of that L-R shift, that's all.

If you are worried still, have someone local visit and test the setup with you to eliminate any doubt. I think that M-S on acoustic git is pretty nice sounding!


Bob



Soundwave Research Laboratories / Crowley and Tripp Microphones :: Ribbon Microphones

[geeek]

Btw the m/s mic looks like a great idea.

If it was made with C&T ribbons, I can imagine it would be fantastic.

If there's ever one developed, I'd like to test it

[broadhurst]

My next amp in the BG series is an analogue m-s processor, with inserts for effects on the m and s channels+ width control and parallel effect mixing, called BG S.I.P.P.[Stereo Image Parallel Processor]
this also removes latency when parallel mixing.
Mick@DAV

[NorseHorse]

Improper imaging with m/s can be caused by miking your guitar too closely. This was what happened when I first ever tried m/s to record an acoustic song I wrote.

This may or may not be the OP's problem, but just thought I'd throw it out there.

[boojum]

To avoid the grief and pain of incorrectly decoding MS signals I use the Voxengo decoder. It also allows encoding tracks which are decoded to regular stereo and you can vary the M and S amounts. And it is free!

You can find it here: Voxengo

[David Rick]

I listened to your first MP3, and I think the M/S pair giving you a fair representation: The left side is louder. Because M/S is a true coincident technique, you can repan it however you want without phase problems. Now if you have recorded a lot of room, you are also panning the room, which might not be what you want.

To avoid this in the future, the thing to do is use a monitoring setup that can decode M/S, and rotate the mic pair until the guitar is centered. Of course, that will cause the M mic to be pointing somewhere different, with results you may or may not like. There are two things you can do about that. One is to use an omni for the center mic, so it won't matter so much where you aim it. Another possibility is to leave the M mic aimed as you like, and just rotate the S mic (still keeping the capsules as close as possible).

M/S technique aside, I hear a pretty distinct sound hole signature, and I wonder if you've tried backing off a bit. A guitar radiates bass frequencies from the whole body, and hearing just the sound hole isn't getting the whole picture. If the room is decent, let it help you hear the rest of the body resonances. Experiment with different player positions until you find a spot where the room is really helping. Then when you widen out the M/S, you'll have something more interesting. When I've recorded guitar this way, I've sometimes even moved additional reflecting or diffusing surfaces around the player to make the image more fun. People don't just play music -- they're always playing somewhere, and you can make that part of the sonic story you're telling if you choose to.

Now if the room sucks, and you're planning to get all your ambience out of a box, then you can just ignore me and carry on.

David L. Rick
Seventh String Recording

[zakco]

Originally Posted by binary

Cheers.. I've done it exactly like that yehh.. I can't understand this shift to the left.. do you guys think it's probably die to more sound coming from the L of the S mic?

As others have mentioned, the loudest point on an acoustic is from the sound hole. Unless you center the mics by pointing directly at the soundhole (yuck...) you will hear one side as louder because...well....IT IS!!!!

I have found this problem to be diminished by increasing the distance from the guitar and as a result, spreading the soundhole a bit...but of course you get more room which can be good or bad...

Where did you point the mics?

[lerone]

Originally Posted by stuntbutt

This may be a product of ITB latency.

Not impossible, but improbable. I would assume that simple hard panning & a polarity inversion would not cause this in PT. Are you sure that the left side of the real stereo field isn't just louder? Assuming everything has been setup correctly (which it seems it has
been) this seems like the only reason why this would happen. Any nearby surfaces, open doors / windows ect?!

Could you post up any files so they could be encoded at our end to see if there are any probs?



Toby

[stuntbutt]

Originally Posted by lerone

Not impossible, but improbable. I would assume that simple hard panning & a polarity inversion would not cause this in PT. Are you sure that the left side of the real stereo field isn't just louder? Assuming everything has been setup correctly (which it seems it has
been) this seems like the only reason why this would happen. Any nearby surfaces, open doors / windows ect?!

Could you post up any files so they could be encoded at our end to see if there are any probs?



Toby

On my native (LE) system, the trim plug has latency. If you use trim on the right side only to flip polarity you have latency on the right side. It makes the left feel louder because it is sooner. I think you are right though, the left is probably just louder because of the close micing distance.

[Ozpeter]

Rather an old question we're re-discussing here??

[springer]

This month's session notes on my webpage is an example of piano using MS. A R122 for Mid and UMT70S for Side.
BTW - the times that I have used the R122 for Side it is well beyond the distance that the offset makes a difference - I think it is like 36" that it only takes effect - otherwise it is fairly even on both sides. Certainly it isn't a 1.8 micron ribbon so it isn't like the SF series but still darn good.

[Bennett Williams]

Originally Posted by Corran

The side mic in an M-S setup MUST be figure 8. The mid mic can be whatever.

Was the left of your acoustic guitar simply louder? I've thought this before but it was simply a product of the acoustics. If the left side of your array was pointing towards the sound hole and the right side to the bridge, it would stand to reason that there would be more sound to the left, correct?

What I would like to know then, is how does the mid/side decoder know which part of the soundwave is out of phase in a figure 8? When I look at a figure 8 microphone, there is only one cable coming out from it, yet a m/s decoder is able to split & phase shift this signal to make the stereo image. Is there a way to fool a mid/side decoder with other setups, and make the result sound like it was recorded in mid/side, even though it may be several microphones?

[John Willett]

Originally Posted by Bennett Williams

What I would like to know then, is how does the mid/side decoder know which part of the soundwave is out of phase in a figure 8? When I look at a figure 8 microphone, there is only one cable coming out from it, yet a m/s decoder is able to split & phase shift this signal to make the stereo image. Is there a way to fool a mid/side decoder with other setups, and make the result sound like it was recorded in mid/side, even though it may be several microphones?

Firstly, it's not "out of phase", it's "polarity reversed". It's not a phase shift, it's a complete reversal of polarity.

Simply, add the mid and side together and you get the XY left channel.

Polarity reverse the fig-8 (ie: swap over pins 2 and 3) and add this to the mid and you get the XY right channel.

It's very simple, really.

Posted via the Gearslutz iPhone app

[panatrope]

It may be easier to get your head around it if you think of the M-S process as sum and difference. With normal stereo, mono is achieved by adding/summing the L and R signals. If you change the polarity of the R signal and then add, it is the same as the difference. In other words the result is what you took away from the L and R signals to make mono.

In M-S micing, the forward facing (normally cardioid) mic is producing a mono signal. The fig-8 mic at right angles to the M(ono) mic is a pressure difference mic. If it arranged so that sounds from the left of the mic give positive voltage out for positive (increasing) pressure, then sounds from the opposite (R) direction give negative voltage for increasing pressure. And because the null of the fig-8 pattern is facing forward, then there is no output for sounds in front.

So summing the M and the S means that sounds coming from the left will reinforce each other and sounds coming from the R will mean that the S voltage will tend to cancel the M voltage - so the sum of the two produces a left-oriented signal. Reversing the polarity of the signal from the S, which is the same as taking the difference M minus S, means that when M and -S are added you will get a right-oriented signal. Of course the ratio of the strength of the signal from the M and the S will depend on how far left or right of centre the sound source is ... just like panning a mono signal.

It is simple, but don't think about it - try it. The results will help make it perfectly clear.

[John Willett]

MS is the same principle as if you add a fig-8 and an omni together you get cardioid.

MS is:-

Fig-8 facing sideways and cardioid facing forwards - add them together and you get a super-cardioid pointing half-left.

Polarity-reverse the fig-8 and add it to the cardioid and you get a super-cardioid pointing half-right.

[Matti]

That was a good way of explaining MS !

Matti

[DCaswellUK]

Originally Posted by David Rick

I listened to your first MP3, and I think the M/S pair giving you a fair representation: The left side is louder. Because M/S is a true coincident technique, you can repan it however you want without phase problems. Now if you have recorded a lot of room, you are also panning the room, which might not be what you want.

To avoid this in the future, the thing to do is use a monitoring setup that can decode M/S, and rotate the mic pair until the guitar is centered. Of course, that will cause the M mic to be pointing somewhere different, with results you may or may not like. There are two things you can do about that. One is to use an omni for the center mic, so it won't matter so much where you aim it. Another possibility is to leave the M mic aimed as you like, and just rotate the S mic (still keeping the capsules as close as possible).

M/S technique aside, I hear a pretty distinct sound hole signature, and I wonder if you've tried backing off a bit. A guitar radiates bass frequencies from the whole body, and hearing just the sound hole isn't getting the whole picture. If the room is decent, let it help you hear the rest of the body resonances. Experiment with different player positions until you find a spot where the room is really helping. Then when you widen out the M/S, you'll have something more interesting. When I've recorded guitar this way, I've sometimes even moved additional reflecting or diffusing surfaces around the player to make the image more fun. People don't just play music -- they're always playing somewhere, and you can make that part of the sonic story you're telling if you choose to.

Now if the room sucks, and you're planning to get all your ambience out of a box, then you can just ignore me and carry on.

David L. Rick
Seventh String Recording

Hi David,
thanks for an interesting and informative post. I have experimented a lot with solo guitar recording, and find it difficult to get a sound that really pleases.
There seems to be a great prejudice against mono recording, but if recorded close, just how 'stereo' is the solo guitar? A mono recording with stereo reverb added can sound better to my ears than an m/s recording..and you are free to place the mic anywhere you like. My own experience of m/s was similar to original posters, leaning to the left. The more side mic you add to the matrix, the more exaggerated this becomes.
The soundfield mic has given me the best results in m/s in terms of a stereo image, and you can greatly vary the pattern/spread to achieve a desired result.
In terms of separate mics, my favourite cardioid for guitar is the dpa 4011, and thanks to OVU for the tip to try pairing it in m/s with the neumann side mic..this is the best blend for the dpa that I have found for my taste.
Recently I tried the josephson c617 omni and was just stunned by the clarity of this mic. Maybe I'll save for another one of these and try a spaced pair or with a jecklin disc for my next guitar recording experiments!
Kind regards,
David Caswell