Logic Pro Direction Mixer: The Mid/Side Trap
When set to MS Mode, the Logic Pro Direction Mixer can decode audio that’s been recorded using a Mid/Side microphone technique. When set to LR Mode, it can pan a regular stereo signal, and easily sum a stereo signal back into mono. Although its interface may suggest otherwise, the Direction Mixer is not a tool for encoding a stereo signal (L/R) into a Mid/Side signal. To illustrate this, I’ll use Mathew Lane’s DrMS.
Head To Head: DrMS vs Direction Mixer
Here’s Jessie J’s ‘Domino’, side signal only, using DrMS:
The same audio bit, this time using the Direction Mixer in L/R mode with Spread set to 2.0:
As you can hear, these are two completely different outcomes. The Side signal that the DrMS plugin produced is mono, since it contains only the difference between the left and right channel. It’s the resulting audio after subtracting the content that’s present in both channels (i.e. the mono audio).
The audio that the Direction Mixer produced in the audio example (with Spread set to 2.0) is still stereo. It just sounds wider, and the mono contents of the audio are still present, although being less pronounced. Logic Pro’s Studio Effects manual calls this ‘extending the stereo base’. This is something completely different! If you’re new to Logic Pro, and new to Mid/Side processing, this is a trap to easily fall into (and for this reason alone, I’ve added it to my Logic Pro X Wishlist).
Don’t let this plugin’s interface fool you.
Note that you can create a Side signal using the Direction Mixer plugin in combination with the Gain plugin:
- Put a stereo audio file on two stereo tracks. Make sure they’re perfectly aligned.
- Put a Direction Mixer plugin on the second track, set it to LR Mode, with Spread set to 0.
- Insert a Gain Plugin on the second track, and invert the phase of both channels.
- The resulting audio is the Side signal.