If you're going to narrow a spread, to then move it around, don't you have do some cancelling in the side the sound is coming from that you want it to move away from ?  I've imagined that Channel Tools did it's thing by playing around with phase to get the cancellation required.  I don't see how else it could work.
 
Someone recently mentioned they didn't like what Channel Tools was doing to their signal phase-wise and I just figured that it was the price to pay for what it does.
 

To be honest I've never used it for anything other than narrowing and positioning - I've never messed with the L/R width controls because I've had no idea what exactly they do. I wouldn't mind hearing about some practical usages...

Paul P
If you're going to narrow a spread, to then move it around, don't you have do some cancelling in the side the sound is coming from that you want it to move away from ?  I've imagined that Channel Tools did it's thing by playing around with phase to get the cancellation required.  I don't see how else it could work.

 
Please see post #12. You can also think of Channel Tools as a more flexible implementation of how Pro Tools uses two panpots, one for each channel, to be able to change the image width and move it around. I'm talking straight level-based stereo applications here, not M/S decoding or anything fancy.

Oh dear - it seems I've opened a real can of worms here. 
 
I lay awake last night thinking of a test I could set up to prove ... er, something.  I've got some ideas I'm going to try later this afternoon.  Not sure what I'm looking for yet, but I promise to report back anything significant.
 
For the moment, I'm going to be skeptical about Craig's claim of being able to place two identical sound sources in the stereo panorama and have anything but a result that sounds like they are at the phantom center between the two points.  I'll just have to play around with the math to prove it - and that may take a bit of thought.
 
MS/LR conversion is totally simple - not a logarithm or trig function in sight.  M=0.5*(L+R), S=0.5*(L-R), L=M+S and R=M-S.  The conversion is lossless - you could convert back and forth all day long and get the same result.  I quite suspect (but have not done the calculations to prove it) that we can use these formulas to prove mathematically that two identical signals at two points in the panorama will reduce to the same result as a single mono signal in the middle (at twice the level).  But like I said, I've haven't sat down to actually do a mathematical proof.  At this point I just suspect my speculation is correct.  So, I guess I'm really setting myself up to look foolish if I'm wrong.
 
Take an edge case where the two mono points are at extreme left and extreme right.  That's two points in the panorama, right?  Now, do you expect to hear anything other than a single placement at the phantom center?  Now, move the two points to the center of the panorama.  Do you expect it to sound any different that the previous case?  Do you expect the content of L and R signals to differ between the two cases?
 
One other thing: the term "pan law" was mentioned earlier.  As far as I know, Channel Tools has no support for pan law, right?  I'm pretty certain it's never mentioned in the documentation.  I just want to confirm that pan law will not be a factor in any testing anyone does.

dmbaer
For the moment, I'm going to be skeptical about Craig's claim of being able to place two identical sound sources in the stereo panorama and have anything but a result that sounds like they are at the phantom center between the two points.  I'll just have to play around with the math to prove it - and that may take a bit of thought.

 
If someone told you on a sunny day that the sky was blue and you didn't believe him, it's true one could use math to show how Rayleigh scattering affects shorter wavelengths, and therefore, the blue light (which has a shorter wavelength) is scattered more by the molecules in the atmosphere. Therefore, the sky appears blue. But a simpler option would be to step outside, then look up.
 
Here's an experiment to lift the veil of skepticism. Use headphones to take room acoustics out of the picture.
 

 

1. Set up something like the above with identical mono clips in each track.
2. Adjust the level for both tracks to -6.0.
3. Pan Track 1 full right.
4. Vary the panpot in Track 2 (circled in red) from full left to full right.

 
At full left, the sound will be centered. As you move it more toward the right, the image width will narrow and shift more and more toward the right until it eventually becomes an extremely narrow point source panned full right. The two Width controls in Channel Tools are doing essentially the same thing, with the added bonus that you can vary the center point from which they extend to the right or left. 
 

Take an edge case where the two mono points are at extreme left and extreme right.  That's two points in the panorama, right?  Now, do you expect to hear anything other than a single placement at the phantom center?  Now, move the two points to the center of the panorama.  Do you expect it to sound any different that the previous case?  Do you expect the content of L and R signals to differ between the two cases?

 
Please see post #12.
 

One other thing: the term "pan law" was mentioned earlier.  As far as I know, Channel Tools has no support for pan law, right?  I'm pretty certain it's never mentioned in the documentation.  I just want to confirm that pan law will not be a factor in any testing anyone does.

This article will tell you what you need to know about pan laws.

oh my...
 
 
 
 
 
 
 
 
 
 
 
... and to think I was using a vectorscope when I shoulda been using my Studio Beats by Dr. Dre.

mike_mccue
oh my...
 
... and to think I was using a vectorscope when I shoulda been using my Studio Beats by Dr. Dre.

Personally, I find the sound quality of a vectorscope lacking. Then again, I find Beatz lacking too...except under 120 Hz, where they're quite tight.

Expanding the width appears to be just adding gain to both L and R in a disproportionate way depending on the pan position, so that as you increase width you get a louder signal panned a bit more towards center.


If you have a meter that shows both L, R and phase (I used IK's) you can see what happens:

Mute R and pan your L signal somewhat in Channel Tools to the left of center with Width at 0 and note the phase (stereo) position on the meter. Now note that when you increase "L Gain" the L volume goes up relative to R such that the phase/position stays exactly the same.

Now increase the L Width without changing the pan position - this time the R volume goes up more than before relative to left and the image shifts towards center.

OK, I did the following test.  I set up a synth (stereo output, no filtering no effects).  I put a square wave in a single oscillator and panned it far left.  Output was as expected.  R channel is totally silent and becomes irrelevant.
 
When I panned the Channel Tools (hereafter CT) to center with zero width, I got a phantom image dead center.  When I expanded the L width control, the output in both channels got about 3 dB louder as I approached the extremes and the phantom center remained dead center.  Metering confirmed both were L and R levels were equal at all width settings. 
 
I froze the track and looked at the waveform.  As expected both L and R were identical and perfectly in phase.  In fact, no phase alteration was ever noticed at any point in this testing (which I think we can all agree is a good thing).
 
When placing the L control about -15 (halfway left) and initially setting L width to zero, here's what happened.  As I expanded the width control, the left channel amplitude stayed nearly constant (increased but only very marginally).  The right channel level increased more.  Frozen waveforms remained identical in all cases except for amplitude (as expected based on what the meter output was indicating).
 
So, I'm going to stick to my guns here and say that in the second case (L at -15), increasing the width changed the stereo image, but it did so by moving the phantom center to the right, and the overall level increased.  One could produce exactly the same result by leaving width at zero, moving the CT L pan position a little to the right and increasing the level slightly.
 
In a situation like this, we've got two identical audio streams in L and R - identical except for amplitude that is.  As we increase/decrease either side, the perceived panorama position will naturally change.  But if the two waveforms are identical other than amplitude, that's all that changes.  That implies that I could produce two exports, one using CT width manipulation and one where I just altered pan and overall output level and I could achieve two exports that are identical.  And if this is true, then there's no width manipulation actually happening.  Changing CT width is just moving the panorama position and messing with amplitude.  Thus, CT width is not doing what it's claiming to do.
 
Anyway, that's my story and I'm stickin' to it. 
 

drewfx1

Now increase the L Width without changing the pan position - this time the R volume goes up more than before relative to left and the image shifts towards center.

Beat me by six minutes, Drew.