how can you isolate the center of stereo for processing?

joninc · Post by **joninc** » Sat Jan 17, 2009 1:31 pm

i am messing around with some DIY mastering today and would love to know if there is a way to treat/isolate/process the center separately from the left and right - plug ins? i am working in cubase 4,

no expensive outboard hardware recommendations please!

joel hamilton · Post by **joel hamilton** » Sat Jan 17, 2009 1:40 pm

joninc wrote:i am messing around with some DIY mastering today and would love to know if there is a way to treat/isolate/process the center separately from the left and right - plug ins? i am working in cubase 4,

no expensive outboard hardware recommendations please!

duplicate the stereo track.
Pan both sides of the track to the center.
Process differently.
Make sure you eother have frame accurate delay compensation, or have the exact same plugs on both channels.
You can get a great sum/difference type situation going on this way.

joninc · Post by **joninc** » Sat Jan 17, 2009 1:48 pm

i don't totally get that - then i am essentially still processing what is/was going on in the left and right tho right? they are just now panned center.

i want to deal with what is in center - snare etc... - in isolation.

dsw · Post by **dsw** » Sat Jan 17, 2009 1:58 pm

would this help?

http://www.waves.com/Content.aspx?id=8885

joel hamilton · Post by **joel hamilton** » Sat Jan 17, 2009 2:39 pm

joninc wrote:i don't totally get that - then i am essentially still processing what is/was going on in the left and right tho right? they are just now panned center.

i want to deal with what is in center - snare etc... - in isolation.

I guess you could get some kind of comparator situation going on...

Collapsing a copy of the stereo file cancels any of the anti-phase info, and then you can use time constats to "mine" what you want from the snare or kick. You wont have the kick and snare separated from a stereo file no matter what you do anyway.
This technique can really solidify the center image. I do it in a mix situation sometimes when the OH sounds a certain way... or the stereo rooms sound a certain way.
Maybe an actyual mastering person will comment on this.
I hope. for your sake. I am not a mastering person.

Scodiddly · Post by **Scodiddly** » Sat Jan 17, 2009 3:12 pm

Do you mean Mid/Side processing? Should be available for free, or there are ways to do it with just regular processing. Look for a Mid/Side (aka M/S) plug in your plugins. The same processing works both directions, it can turn Left/Right into Mid/Side and turn Mid/Side into Left/Right. If you go L/R to M/S the mid should show up on the left channel output.

argonautlabs · Post by **argonautlabs** » Sat Jan 17, 2009 4:15 pm

How to extract Mid and Side data without plugins or outboard gear by Me:

Joel is correct. mid channel is simply the addition of R+L. information present in both streams becomes twice as loud as stereo only information. for the side channel its R-L. information present in both streams is canceled, leaving only sides. the decoding can be mathematically shown below.

M = R+L;
S = R-L;

Right Channel From Mid and Side: (M+S)/2 = ((R+L)+(R-L))/2 = 2R/2 = R
Left Channel From Mid and Side: (M-S)/2 = ((R+L)-(R-L))/2 = 2L/2 = L

Addition is obviously just the sum of the signals in the mixer, subtraction is just the sum with the second channel 180 out of phase.

So basically you would change your R:L signal to M:S using the first set of equations. Apply processing, then go back to R:L using the second set of equations.

To explain further:
I know you don't want any stereo data present in the Mid at all, but technically what you are trying to do is reconstruct three channels (L:C:R) from two (L:R). Because the signals' information now overlap each other it is seriously difficult to extract that information. Think of the case of summing two instruments to a single track. The only way you can now extract the two purely is by filtering based on the instruments properties (like frequency spectrum or time present or something). This is why most "vocal removers" don't work too well. I would suggest trying the Mid side method above, it will probably separate it enough to get the results you want.

~Nathan

ashcat_lt · Post by **ashcat_lt** » Sat Jan 17, 2009 5:27 pm

Voxengo MSED (Mid/Side Encode/Decode) is free.

cgarges · Post by **cgarges** » Sun Jan 18, 2009 7:02 am

joel hamilton wrote:duplicate the stereo track.
Pan both sides of the track to the center.

I never thought of that as a way to encode MS. Thanks, Joel! Very cool.

Chris Garges
Charlotte, NC

SaneMan · Post by **SaneMan** » Sun Jan 18, 2009 12:41 pm

What about bussing everything thats just in the center("snare, etc.") to a mono track and adding that to your stereo track, processing it as you like. Or if everything thats panned is hard L/R, just reprint it as a stereo L/R track and a mono C track. Or just three mono tracks. Really you should probably just do this in the mix, with a subgroup for you C elements, getting them to a place where when you go to master you'll be happy with how they sit in the mix. But as you say, there are no rules

joninc · Post by **joninc** » Mon Jan 19, 2009 1:57 pm

thanks for all the info and explanation guys,

i don't have access to the mix files - just the master.

(and even if i did it's a pretty minimal lofi type recording - drums kick/snare/rm - were bussed to 1 track!)

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how can you isolate the center of stereo for processing?

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