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How to read a Phase Scope...

Profile picture for user mark_van_j
Submitted by mark_van_j on Sat, 10/18/2008 - 18:54

I just started getting into these things after I downloaded a sexy little free plugin called "Stereo Tool" by Flux. http://www.dontcrac…

Problem is, I don't really know what to look for. It's pretty clear what the squigly lines stand for (M/S?), though I'm more curious as to the meter at the bottom which has -1, 0, +1 written on it. A mix I'm working on atm has the meter about 4/5ths of the way to +1 for most of it. What does this mean? Should it be at 0 (as a voice inside me is quietly telling me?

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Profile picture for user Space
Space

"Stereo Tool features ultra precise controls of input gain and individual pan for left and right channels. A phase inverter is available for each channel. A global stereo pan and a stereo width settings are also implemented to complete the management of the stereo signal.

Stereo Tool also offers an accurate visual feedback reflecting the signal content. A vector scope display, PPM meters for both inputs and outputs, and a phase correlation meter permanently monitor the signal.

Inserting our Stereo Tool after a Bitter Sweet II will open your mind about all the possible manners to control the stereo stage. "
Download Now

Sun, 10/19/2008 - 01:32 Permalink
RemyRad
RemyRAD

Phase Scopes have been utilized since the dawn of stereo. It certainly was an imperative when cutting to disk as heavy out of phase content would wreak havoc for the cutter head. So even though much recording is mostly of a random phase nature, i.e. orchestral recordings, not so cut & dried for popular music, rock-and-roll, country, etc., where many more phase errors can be made.

The phase can be displayed in different ways on a scope and software gives you even more choices. Just know, you don't want too much stuff that is 180° out of phase, no matter how wide you think the stereo sound's. It will just all disappear upon Mono playback. And you don't generally have to worry about cutting into lacquer.

Lick that lacquer (it's made from dead bugs)
Ms. Remy Ann David

Mon, 10/20/2008 - 07:26 Permalink
Profile picture for user mark_van_j
mark_van_j

Here we go... After fruitless searching on wikipedia and google, I happened to come across this explanation on Izotope's site. Pretty much sums it up:

The correlation meter indicates the degree of similarity or correlation between the left and right channels.

When the audio in the left and right channels is similar, the meter draws towards the right. The extreme case is when the left and right channels are exactly the same, in which case the correlation is +1 and the meter would be positioned all the way to the right.

When the left and right channels are uncorrelated, or very different, the meter draws towards the left. The extreme case here would be for the left and right to be exactly out of phase, in which case the correlation is -1 and the meter would be positioned all the way to the left.

As the correlation meter updates, it "paints" a history to show the correlation of the left and right channels over time. Brighter regions indicate that the correlation meter has spent more time in that area. This provides you with a quick way to visualize the extremes of the phase correlation as well as the most common regions.

In general, most recordings have phase correlations in the 0 to +1 region. A brief readout towards the left side is not necessarily a problem but could represent a possible mono compatibility issue.

Note that as you apply greater multiband stereo widening or reverb width to your audio, the phase correlation will tend to draw more towards the left side, as the left and right channels will become "wider" or less similar.

And as for the vectorscope:

Typically, stereo recordings produce a random pattern that is taller than it is wide. Vertical patterns mean left and right channels are similar (approaching mono, which is a vertical line). Horizontal patterns mean the two channels are very different, which could result in mono compatibility problems.

Tue, 10/21/2008 - 14:33 Permalink