Keep an eye on your stereo phase correlation
There are lots of effect plugins out there that abuse phase to achieve stereo widening effects. With very few exceptions, if a plugin has a “stereo” knob, it’s throwing some stuff partially out of phase on one side of the stereo image (or often both) for settings >100%.
This is a super cool effect — it can sound 3D, like the sound is outside your speakers even. I use it a lot.
But you don’t necessarily get this for free! It can screw up your mix if you’re not careful, in ways that you might not even be aware of if you’re not vigilant.
Specifically: effects that are created by manipulating phase aren’t always mono-compatible. When you throw some or all of one channel of a stereo signal intentionally out of phase to some degree, it will cancel to some degree with the information in the other channel. Like this:
And when this cancellation happens, it reduces the amount of that signal in the center channel, sometimes to zero — meaning that this sound, that’s so awesome and wide in stereo, might be significantly quieter or even completely absent when listened to in mono!
I can imagine someone reading this and being like, “Who cares? People haven’t listened in mono since the 70s.” To which I would reply: bluetooth speakers. They’re ubiquitous, and many of them are a single speaker that sums the incoming signal to mono.
Some reverbs also have some amount of phase incoherence between the left and right sides of their stereo image, so that’s something else to look out for. It’s super frustrating to spend time dialing in the perfect vocal reverb, only to have the vocal sound dry and wrong on a bluetooth speaker!
So, what to do? The answer is super simple: use a phase correlation meter. Here’s an excellent free one, and here’s my tutorial on how to use it.
I personally use bx_digital v3 by Plugin Alliance — I prefer the ballistics on the correlation meter, and also it has a stereo knob built into the plugin, which makes it a one-stop shop for dialing in a mono-compatible stereo image.
(bx_digital v3 is on a really good sale as I write this, by the way, at the link above! It’s a killer mid-side mastering-grade EQ; very transparent. I use it all the time.)
I tend to put an instance of bx_digital v3 at the bottom of the plugin chain on anything that might exhibit phase correlation issues, and I just keep checking in on how that correlation meter is doing as I’m dialing in the sound. If the correlation goes much below 0.5, I turn the stereo knob to the left to narrow the stereo width until the correlation is in a happier and more mono-compatible place.
Stereophonically — jamie
