Stereo Mid-Side Chess Test

Transcription of the video above

How well do you really understand audio engineering? This is a really great way to test how you put two ideas together. Stereo isn’t just split between left and right, it can also be split between sides and center. This isn’t hyperbole, it’s literally the way a record player works. Armed with a single stereo track, a basic command of signal flow and the most basic utility plug-in, you can do some mind bending manipulation of your stereo image. Once you know how to do it, you may decide you don’t need or want stereo enhancement plug-ins anymore.

So if this is the right side and this is the left side, where’s the center? As it turns out, the center is just a combination of the left and right. The middle is just whatever’s common to both sides.

Here’s your first simplified recipe. We’re going to take this stereo track and this is going to be your source and what you’re going to do is to duplicate it. So in hardware or in your DAW, this single source is going to feed two tracks. And what we’re hearing is no longer this, but this plus this. Your first magic trick happens when you take one of those copies and combine them into mono and then invert the polarity. What happens as you bring the level of this up is that you split this signal and whatever was in the middle will disappear and you’ll just be left with the sides. No vocal, no snare, no bass, no kick. You can adjust the level of this up until it’s the same level as the source and you can selectively widen or cancel the center, but it doesn’t give you the same kind of control as a true mid-side matrix.

And to do that, we need to add another layer to this, which is why every engineer needs to get comfortable not just with phase and polarity, but with routing signals. To get them to go where they want them to be when they want them to be there. In this scenario, we need a few more copies. So most likely, you’ll be busing or multing this here, here, and here. Three copies.

Stereo can be described as both the sum and the difference between two channels. What we perceive in the center is the sum. And to understand what’s on the side, we need to subtract one side from the other. Left plus right, left minus right, both of these summed to mono, but this one with one side inverted. And what about that third track? This track will also be summed to mono or pan to the center, but instead of left minus right, it’s going to be exactly like this one, but now the entire thing inverted.

This is your recipe for a mid-side matrix. You’re going to combine these together, left center right. This recipe can be used to process the center separately from the sides. You can even widen the stereo image to the point where it sounds like the sound is coming from beyond the boundary of the actual speaker. The problem is your center will suffer. Make no mistake. This is some powerful sorcery.