I’m wondering if anyone knows the answer to how Channel Tools manages to pull off its L and R individual width adjustments.  I fully understand how M/S alterations can let one manipulate the overall width and placement of a stereo signal.  But what I can’t conceive of is how the individual width adjustments on the L and R controls (the little knobs beside the main one in the L and R sliders) can actually do anything.

Consider this thought experiment.  Assume the R channel is complete silence.  It doesn’t matter where we place it using Channel Tools, it should have zero effect on the output.  Now, put the L slider at dead center.  This is a mono signal.  How can adjusting the width of L do anything?  The information is not present.  No matter how “wide” we set the width control, there’s still just a single (mono) signal.

We give a mono signal fake width only by manipulating it and coming up with two similar but not identical mono signals.  We can use delay, verb, EQ or a variety of other tricks to do this.  But there’s no way to take a mono signal and widen it without creating two non-identical signals.

Yet, Channel Tools claims to be able to do this.  The documentation tells us nothing about what’s going on under the covers.  Is Channel Tools engaging in some signal manipulation trickery and not telling us what it is?

Before I get in and do some rigorous testing to solve this mystery, I thought I’d ask if anyone has previously done some investigation and figured it out.  I hope this question is making sense.

You might want to ask Craig,
 
He uses the word "width" 6 times in one paragraph:
 
http://www.soundonsound.com/sos/jul09/articles/sonarworkshop_0709.htm
 
but I still don't quite know what "width" means in this context.
 
When I use Waves S-1, which has a width control, the "width" effect seems to be provided by very subtle delay to the far side of the "width".

Here's an example of what I mean about S-1:
 
http://forum.cakewalk.com...-Imaging-m2850597.aspx
 

dmbaer
 
Before I get in and do some rigorous testing to solve this mystery, I thought I’d ask if anyone has previously done some investigation and figured it out.  I hope this question is making sense.

Channel Tools is designed to work only with stereo or M/S signals.

mike_mccue
You might want to ask Craig,
 
He uses the word "width" 6 times in one paragraph:
 
http://www.soundonsound.com/sos/jul09/articles/sonarworkshop_0709.htm
 
but I still don't quite know what "width" means in this context.

 
The context was in the paragraph's first sentence - "There's also an alternative panning control option." So width refers to the stereo imaging associated with panning.
 

Anderton
 
Channel Tools is designed to work only with stereo or M/S signals.

Yes, I quite understand, but that's not my question.  If you have a stereo signal and want to narrow it, convert it to MS and multiple the S by some factor like 0.5.  If you want to then skew it to one side or the other add or subtract, depending on which side you're aiming for, X*M to/from S, where X will govern the amount of skew.
 
Now, when we're talking about manipulating the width of just L or R, as Channels Tools promises to do, these tricks won't work.  L and R are not stereo signals to begin with.  Thus my question.  How can we have independent width controls on L and R.  They are individually mono signals and we can't convert them to MS to accomplish the above trickery (well, we can but M will be the original signal and S will be silence so there's nothing to be gained).
 
Am I making more sense?

Anderton

mike_mccue
You might want to ask Craig,
 
He uses the word "width" 6 times in one paragraph:
 
http://www.soundonsound.com/sos/jul09/articles/sonarworkshop_0709.htm
 
but I still don't quite know what "width" means in this context.

 
The context was in the paragraph's first sentence - "There's also an alternative panning control option." So width refers to the stereo imaging associated with panning.
 

 
 
I'm no closer to understanding what you mean than I was the first couple times I read it.
 

Anderton

dmbaer
 
Before I get in and do some rigorous testing to solve this mystery, I thought I’d ask if anyone has previously done some investigation and figured it out.  I hope this question is making sense.

Channel Tools is designed to work only with stereo or M/S signals.

 
Luckily even "mono" tracks in SONAR dump straight in to a Stereo, or two track bus. That probably why the mono "mid" integrates into Channel Tools M/S matrix so easily. 

Hi David, FWIW I think you have posed an interesting question.
 
I just generated a 120 second long custom fabricated "stereo" test tone with Adobe Audition.
 
The tone had a 600Hz sine wave peaking at -6dBFS on the left and it had a 1200Hz sine wave peaking at -6dBFS on the right channel.
 
I imported the tone track into SONAR and placed an instantiation of Channel Tools on the track.
 
I placed an instance of NUGEN's Visualizer on the master bus.
 
I used Visualizer's Stereo Spectrum Analyzer and I used the Vector Scope.
 
When I brought either the right or the left halfway, or a 15 degree angle, with minimum "width" I could see the amplitude on the Stereo Spectrum Analyzer change appropriately and I could see the tilt on the vector scope.
 
When I left the center at the 15 degree angle and maximized the width so that the far side was at the limit I noted that the amplitude of the side being adjusted decreased by approximately 2dB, ( which was not substantially different then simply moving the L or R closer to the center a couple more degree) and there was a very slight increase in the spread on the vector scope which would indicate that there is some aspect of widening occurring with a very slight phase shift or very short delay.
 
Interestingly, if you adjusted the width for a spread further than 30 degrees the results seemed to mimic the effect of simply adjusting the L or R closer to its respective mate, because of course to spread the width further than 30 degree you had to move the L or R so as to get enough spread from the closer of the two side limitations.
 
I'd have to run some more tests before I thought that I, personally speaking, understood what was going on, but my gut feeling is that "not much" is close to an accurate description.
 
I would be curious to learn what others discovered, thought, knew etc.
 
Thank You.

mike_mccue

Anderton

mike_mccue
You might want to ask Craig,
 
He uses the word "width" 6 times in one paragraph:
 
http://www.soundonsound.com/sos/jul09/articles/sonarworkshop_0709.htm
 
but I still don't quite know what "width" means in this context.

 
The context was in the paragraph's first sentence - "There's also an alternative panning control option." So width refers to the stereo imaging associated with panning.
 

 
 
I'm no closer to understanding what you mean than I was the first couple times I read it.

 
Channel Tools has a Panner Control section. The two "pan" controls are called L and R and are calibrated by angle (the pan position). Each pan slider includes linked controls to the slider's left and right that set the width (i.e., the percentage of the stereo image covered by the left and right width controls). It's probably easiest to understand how the following works if you open Sonar and do the steps. 
 
1. Set the L pan to center, and angle to 30 degrees.
2. Slide L pan toward the right. At some point, the right width control will butt up against the end of the stereo field. 
3. If you continue rotating L pan toward the right, the right width control can't move any further. So the stereo image width will shrink because the left width control will continue moving toward the right - it hasn't hit any limit. The pan control remains in the centre of the available amount of stereo image width. 
4. However if you hold Shift while moving the pan control, when a width control hits the end of the stereo field, you can't move the pan control any further. This is helpful if you want to lock a signal to a particular stereo image width.