Mid Side Processing:
The Basic Set Up

Mid Side processing involves working independently with the sum and difference of the left/right channels of a stereo mix file.

With mastering software it's very easily accomplished through a free Voxengo plug-in called 'MSED'.

Software is also available from Waves S1 plug-ins, and PSP's Stereo Controller plug-in, to mention just a two.

In WaveLab you have two options (1) the Stereo Expander; or (2) for more precise control with some numerical feedback use the Tools One plug-in set up the following way:

Open up two instances of the plug-in in series; set both faders in each to -6.0 dB, and engage the 'MS' option in each. By holding down the ALT key, you can move the faders independently of each other allowing you to the adjust the width, or narrowness, of the stereo image.

For ultimate control, follow this procedure:

Load your stereo file into your DAW. Then place a copy of that file in the next track below.

Insert Voxengo's MSED plugin in the top track and pull down (mute) the side channel. This lets you work with the sum of the left and right channels. In other words the mono element of the mix.

Do the same with the copy track just below only this time pull down (mute) the mid channel. This lets you work with the difference of the left/right channels – the stereo element of the mix.

With a set up like this for instance, you can pan the stereo element of your mix (the lower track). This lets you even out the left/right balance of the mix without disrupting the placement of centred instruments.

Now here's a fun trick to play with on some of those “bad” '60's mixes – you know drums right, vocals left sort of thing:

Using the DAW set-up described above, delay the side element of the mix by 6 to 10 milliseconds!

You should hear a fuller, wider, and more centred mix.

You won't, however, get any specific instrument placement.

Which leads me to this extremely important warning about what I refer to as de-correlation:

It is absolutely imperative that the mono and stereo elements of this DAW set up remain locked in timing right down to the smallest sample.

In other words they must begin at exactly the same time, other wise you'll begin to lose any imaging or localization in the mix. You can hear problems like this immediately even if the shift is only by a sample!

Because of this I would advise to use only linear phase type EQ's; and compressor's which do not have any type of analogue modelling characteristics designed into it.

Unless of course the resulting image smear sounds acceptable to you.

As I said mid side processing is a very powerful technique, but it can lead to 'destruction' if the above caveat is ignored!

So use wisely.

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Mid Side Mastering

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