what youre looking for is a Phase Correlation Meter. It subtracts the left from the right channel (or vice versa) in real time and displays values between -1 and 1.
If youre in the negative range, you will experiencing phase cancellations, if youre in the positive range youre experiencing phase amplifications.
Ideally you want to stay near the center (zero) preferably more towards the center-positive side.
Most DAWs come with one, if not, there are vsts, do a google search now that you know what its called.
