Could someone explain the Phase Scope behavior?

I understand signal phase, at least I thought I did. However the Phase Scope meter puzzles me. FWIW, looking at a stereo track, I can visually see that the Left wave is slightly larger than the Right wave, maybe 1db, and this has to figure into the process but I am not clear that it does because the Phase Scope is not centered on ‘0’ - and actually…shouldn’t this make the Phase Scope indicate that the Left wave is more dominant than the Right wave in the Phase Scope?

As I look at the Phase Scope I see the shifting orange image as the wave plays and is seems centered. However below the orange image, this is my area of question. As the stereo track plays there are indicators, -1…0…+1, and then a green vertical line with two red vertical lines on either side of it that fluctuate as the file plays. The green line never goes below the ‘0’ mark and typically exists centered in the 20% range (two bumps to the right of the ‘0’, towards the +1. If I mute the Right wave, this green vertical line shifts immediately towards the Left side of ‘0’, which seems a given, and the orange image presents a somewhat 45 degree thick-ish line image. Which makes sense, correct?

So what am I missing here?

On the bottom, +1 is perfect phase correlation between the left and right. -1 is perfect 180 degree phase cancellation (if summed to mono) between left and right… In general on mixes, phase correlation is rarely perfect (unless someone mixed in mono on purpose) - hence the reason the lines on the bottom part of the phase meter move around a little… The further right the little green line, the more “mono” the mix… Further left the little green line, the more “stereo” the mix.

On top, a straight up vertical line indicates perfect mono - and a horizontal line indicates perfectly out of phase (the opposite of mono). Mixes with patterns that are mostly along the vertical line are very mono mixes in general… mixes that have a much wider pattern are more “stereo”… They have more out-of-phase information between the left and right channel, and indicate a wider sounding mix. DO THIS: Open a standard commercially released mix. Then load the “stereo expander” plugin. Drag the slider all the way to the left (the mix is now mono), and look at the meter. Now drag it all the way to the right and look at the meter… Now experiment with settings somewhere in the middle, and you’ll begin to understand the meter. Now, DO THIS: slide the “stereo expander” slider all the way left again (so the mix is mono). Keep that setting, and then just under/after that plugin, load the “stereo tools” plugin. In there, click “invert left phase” (while listening to the mono version of your song), and watch what happens… then uncheck it… See how it all works? That should explain it pretty good.

Be careful with widening though… It can be really nice upon first listen, but sometimes certain elements will suddenly be too loud in a mix… and it may even give a slightly less “powerful” feel (less perfect correlation between both speakers playing the exact same thing). This can be good/bad. Use cautiously to good taste.

It’s correct - I guess I didn’t clarify well enough. I was referring to the bottom part of the phase meter. I just edited my post above to show I was referring to that.

Ah, OK, got it. Thanks toader!

The WL manual has a pretty good section about it too: page 424 - also for the settings of the meter.

This explains the various types of phase/vector scope displays


Thanks Arjan and Thomas.