I would think that if you're going to do this, it's probably a good idea to make sure that your "sides" are very mono compatible, because if they're not (i.e. they sound phasey when collapsed to mono) and you're attenuating the solid "mid" component then I suspect it would make things sound even less solid in mono.

I think I'd be more likely to use a mid-side EQ to notch out some important vocal frequencies in the middle. NI's Passive EQ is good for this.

cparmerlee
My only confusion about these plug-ins that support mid-side is that they don't really give you much (or any) control over where the boundary between mid and side lies.  I think Channel Tools can do that, so I guess you could create two buses and use Channel Tools to separate mid from side, then apply EQ to the mid bus, which I think is what Bitflipper is suggesting.

That's because there is no boundary as such. "Mid" means all the components that are the same on both the left and the right channels. "Side" means all the components that are different between left and right. Subtract left from right and multiply by 2 and what you're left with is whatever they had in common. It's a straight-up arithmetic operation, not a gradual transition.
 
Of course, most components are not exclusively left, right or center. A mono track panned 50% left still has content in the right channel, so is it going to show up in the Mid or the Side? This, I think, is the confusion you're referring to.
 
The answer is that it's both Mid and Side. Whatever portion of that track's amplitude that is common to both channels falls into the Mid component and the part of it that's different falls into the Side component. Remember, we're not talking about discrete instruments here, but percentages of amplitude across the frequency spectrum. In this example, you'll still hear that track when you solo either the Mid or Side, because it's both.
 
So what happens to that track when you raise the Side component using Channel Tools or MSED? Assuming the left and right channels are spectrally identical, you'll simply be exaggerating the L/R volume difference. In other words, panning it further to the left. If it had been a one-track mix, you could have achieved the same end with the pan slider.
 
But this track is likely part of a whole mix consisting of other elements that are each panned differently and that have different spectral content. Consequently, raising the Side is more complex than simply exaggerating all the pan positions in your mix. It's also going to redistribute frequencies across the panorama, because some frequencies are going to be more similar left-to-right than others. Effects such as reverb (both artificial and natural), chorus and delays all contribute to subtle left/right imbalances that will be emphasized by raising the Side.
 
On a full mix, making room for a vocal by lowering the Mid portion often makes more sense than raising the Side. But using M/S EQ makes even more sense. Why turn down center-panned frequencies that don't conflict with the vocal? You'd just be losing things like kick and bass that weren't hurting anyone to begin with, and are necessary to keep the energy up. With Mid/Side EQ, you can lower just those frequencies that would otherwise mask the vocal, while keeping the lows and highs intact.
 
If you want to take it one step further, there are plugins that transparently make room for the vocal by dynamically dipping only conflicting frequencies and leaving everything else alone. 
 
 
 
 

My apologies.....I will rethink my answer.

sharke
I would think that if you're going to do this, it's probably a good idea to make sure that your "sides" are very mono compatible, because if they're not (i.e. they sound phasey when collapsed to mono) and you're attenuating the solid "mid" component then I suspect it would make things sound even less solid in mono.

One great aspect of binaural panners is they collapse properly into mono, because of the way the accentuation is derived in the first place from a mono signal.

Waves has a cool program called "Center" which could help.  I think it's designed for full mixes, but should work on the master buss.
 
http://www.waves.com/plugins/center
 

bitflipper
most components are not exclusively left, right or center. A mono track panned 50% left still has content in the right channel, so is it going to show up in the Mid or the Side? This, I think, is the confusion you're referring to.

Yes.  Thanks.
 

bitflipper
If you want to take it one step further, there are plugins that transparently make room for the vocal by dynamically dipping only conflicting frequencies and leaving everything else alone.

The so-called "dynamic EQ" products.  And I guess it follows that the best of all worlds might be to do dynamic EQ on vocal-sensitive frequencies ONLY on the MID portion.  I think Ozone can do that, but I have never tried it.

kellerpj
bitman:
Interesting.  I'm interested in what you said because I often mix in headphones.
What do you mean by the phrase "stacked low to high on each side"?
 

Like mixing in mono, sounds are stacked more or less according to frequency range trying to make certain there is little overlap if possible for greater clarity and less masking.

Another way to make room for vocals is to use dynamic EQ. So when a threshold level in a certain spectral range is met then the equaliser will dip or expand. Using Mid/Side assignments you can decide if you want to increase the mono component of the vocal track or decrease the sides in that area. Note, this only triggers when the vocal happens.
 
Also it's worth noting you can do this with Cakewalk LP EQ however I don't feel my aging PC can handle the power it requires especially if there is lots of other things going on.
 

Also mixing on headphones can be deceiving. Sure it can be done with the right effects and environmental emulations like Focusrite VRM, Waves NX (which now supports some common headphone models) and Sonarworks Reference 3 which I personally use as it it uses eq correction and allows you alter the response of the bass and slope? of the headphone response.
 
Anyway happy mixing.

If you know what you want to lower then what about side chaining compression to make the offending material duck under what you need the room for.
 
Like side chaining a guitar with compression to duck under Vocals.