Stereo Miking Techniques (M/S help please!)

[Seth Bloombaum]

Originally Posted by Gary Nattrass

...I have also been lucky to use an AMS Neve digital console for most of my dubbing career and it actually has an M/S control on it for stereo A/B signals so that you can adjust the width of any stereo source in post...

I was reading along in Gary's post, ready to protest "but if you don't actually record your M/S signal, but decode it to L/R, you lose the ability to adjust apparent stereo width in post!", one of the really cool things about M/S technique.

Gary, are you saying here that this particular console can recode L/R back to M/S, adjust width, then matrix back to L/R? I think I've heard of this trick, but if anyone has further details on how to accomplish the de-matrix of L/R back to M/S I'd be very interested to learn more.

This is all assuming an original M/S source...

[Jim Andrada]

Seth,

Take a look at Waves SI - you can change the stereo spread of any A/B stereo track.

There's also a plug in from Brainwerks in Germany that does it (and is cheaper/no dongle)

I think that they effectively transform the A/B tracks into M/S then change the spread, then retransform

[Gary Nattrass]

Yes guys the AMS Neve Logic and DFC digital consoles have two controls on stereo channels that can zoom the image from mono out to 180 degrees, they can also matrix M/S but as I mainly record A/B I just to us the width control to widen or make narrower the stereo image.

I am now on pro tools and I have a free plug in called bx-solo from brainworx that can do the same job on any stereo A/B signal:http://www.brainworx-music.de/index....6&um=2&lang=en

All stereo A/B signals follow the M/S principle of
M=Mono
Left= M-S
Right+ M+S

So if you increase the S content it will widen the stereo image and if you decrease the S signal to zero you will get mono.

The original Dolby pro logic also works on this principle where the signals are as follows:
Left=M-S
Centre=M
Right=M+S
Surround=S (two rear speakers in mono but with filtering applied)

Hope that all makes sense.

[John Willett]

Originally Posted by Gary Nattrass

M=Mono

Actually M = Mid (*not* Mono)

MS = Mid and Sides

But you are correct in saying that L=M+S and R=M-S.

Going the other way:
M=L+R
S=L-R

[Seth Bloombaum]

Originally Posted by John Willett

Going the other way (dematrix):
M=L+R
S=L-R

Ah, John, thanks for going back to the math. Now I get it! I can set up a dematrix in my NLE next time I get a recording from an M/S mic that has an internal matrix to L/R.

[Jim Andrada]

OK - found the link to Brainworx Solo. I use Waves SI on my main system but I installed this on my notebook so I don't have to schlep the Waves Dongle around with me.

Take a look - nice plugin for the price (free!)

MS-Mastering Tools by Brainworx-Media

[John Willett]

Originally Posted by Jim Andrada

Take a look - nice plugin for the price (free!)

Personally I use the Voxengo (free) MS plug-in.

[Bob Grant]

I've used both my own Rode NT4 X-Y mic and a 'loaned' Sanken CMS-10 phased array mic to record live music and drama events. The Sanken can also be switched into hypercardiod in which mode it is a very capable shotgun. It's an expensive beast, it is quite short as it was built to go on a camera although I've always used it on a stand.

Decoding M/S in post is pretty easy, took me less than 10 minutes to nut out how to build a M/S decoder in Vegas, no plugins required.

What has not been mentioned here at all is any stereo recording technique relies totally on microphone placement. As I've learnt the hard way this is critical. A few inches or a few degrees can make all the difference.