Correlation of stereo signals

[Farshad]

Hi all

My question is about correlation meters in audio analyzers (i.e. Roger Nichols, etc) that have a range from -1 to +1:

My understanding is that a correlation of:

+1 means mono signal
0 means perfect stereo signal
-1 means out of phase signal

So is it correct to say that as long as the correlation between the left and right channles of a stereo signal stays between 0 and +1 there will be no phase issues?

Peace

[MASSIVE Master]

There are *always* phase issues in a stereo signal -- assuming the signal is more than a guy saying "left" into the left side and "right" into the right side. Once he says them both at the same time, there are going to be phase issues.

It's not a dirty word or anything --

Whether those phase issues are "nasty" and will result in a recording that falls apart in mono is up to you. A meter is only a guide (which like RTA's and the like, are rarely ever used). Your ears will tell you if the result is acceptable or not.

[Edward_Vinatea]

Originally Posted by Farshad

My understanding is that a correlation of:

+1 means mono signal
0 means perfect stereo signal
-1 means out of phase signal

So is it correct to say that as long as the correlation between the left and right channles of a stereo signal stays between 0 and +1 there will be no phase issues?

Peace

Hmm - meters only read positive for positive correlation and negative for negative correlation. They shuould also display the cosine of the phase angle between the two channels. In Gonio the cosine between '0' and '+1' represent positive correlation. In phase content is thus identified between '0' and '+1' while out of phase content between '0' and '-1'. These types of phase meters are used by audio professionals day in and day out.


Regards,

[Sunbreak Music]

Phase issues should be immediately recognizable by an ME. While I'm more sympathetic to people viewing spectral content, phase issues should leap out upon first listen and shouldn't have to be verified by metering.

You can train yourself to hear this sort of thing w/ a simple delay. Set one channel dry, the other at around 20ms, and starting listening as you increase the delay time on the "wet" channel. It's simple, but gets you started. Ocassionally collapse to mono to hear what effect it's having on different parts of the mix.

You'll get it.

[Farshad]

Thanks for the replies guys. I can actually tell by ear when I hear a phase problem. I was trying to enhance my use of a phase meter.

Cheers