Mid-Side Processing

In my post on Mid-Side microphone technique, I mentioned that some people like to use this type of miking because it allows you to process the mid channel and the sides separately, but as I mentioned there, you can do this with any stereo track, regardless of how it was recorded. Mid-side processing is used by mastering engineers quite a bit, because full mixes are prime candidates for such tricks. For example, let’s say a mastering engineer is working on a a stereo mix where the sound of the high hat and cymbals is too bright. He/she could just turn down the high frequencies of the entire mix, but that would make the vocals sound duller, it would make the kick and snare sound less snappy, and who knows what else. With mid-side processing, the engineer can just eq the sounds that are panned out, and everything that’s panned in the center (usually the lead vocal, kick, snare, and bass) will remain unaffected. The farther away from the center something is, the more it will get affected. Overheads are usually recorded to have a fairly wide sound, so they will get eq’d nicely when adjusting the side channel of an M-S pair. Yes, anything else that’s panned out will get eq’d too, but at least we’re sparing the important stuff that’s in the center. This is just one neat trick you can do using this technique. The first time I saw an audio engineer do this, I thought he was performing black magic. Let’s figure out some ways to practice this sorcery…

There are three ways to do mid-side processing on any stereo track. The simplest way to do this is to use a plugin that has a mid-side matrix built in. Companies like brainworx use this as their angle. They will, for example, put an eq inside of a M-S matrix, so that you can easily eq the mid channel or the sides. But you don’t have to run out and buy these plugins if that’s what you are trying to do. You can easily MacGyver this for free: Just insert a M-S encoder/decoder (in the encode setting), follow that with an eq (or any other plugin), and then follow that with another M-S encoder/decoder plugin (in the decode setting this time). Just make sure to use the “Multiple Mono” version of the EQ plugin, then unlink the left and right channels so that you can adjust their settings independently, and there you go. The left channel of your EQ now controls the center channel, and the right channel of your EQ now controls the sides. The unfortunate effect of using this technique is that you are using up 3 plugin slots instead of one, but the cool thing about this is that you don’t have to buy any specialized M-S enabled eq plugins. Also, you can do this with any effect you have in you DAW, so you can really get creative. M-S encoder/decoder plugins are out there, and some are free. I use the +matrix plugin from Soundhack. It’s available for free as a part of the freesound bundle. In addition to this one, I also like to use the Waves S1 Stereo Imager plugin. It’s got some nice tweak-ability, but it ain’t free.

There is also a third way to use this technique: You can set up a mid-side matrix in your DAW or on your console, by using routing and a few phase switches. The major advantage of using this technique is that it’s totally old skool, and you’ll be able to feel totally bad-ass about yourself. The main dis-advantage is that it’s not only a somewhat involved and tedious process to set up, but it’s totally unnecessary. Because of this, I’ll leave it out of this blog post. Maybe one day, if I really run out of things to write about, I’ll make a blog post about this third technique.