Re: [LAD] Mixing audio: Implementing pan and balance

On March 12, 2013 08:41:01 PM you wrote:
> On 03/12/2013 04:23 PM, Tim E. Real wrote:
> > Hi, I need some advice, clear up some confusion:
> >
> > I noticed our app uses this pan formula:
> > vol_L = volume * (1.0 - pan);
> > vol_R = volume * (1.0 + pan);
> >
> > where volume is the fader value, pan is the pan knob value
> > which ranges between -1.0 and 1.0, and vol_L and vol_R are the
> > factors to be applied to the data when sending a mono signal
> > to a stereo bus.
> >
> > When pan is center, 100% of the signal is sent to L and R.
> > At pan extremities, the signal is boosted by 3dB.
> >
> > But according to [1], we should be using a Pan Law [2],
> >
> > where pan center is around 3dB to 6dB down and pan
> > extremities is full signal.
> >
> > So I want to change how we mix mono -> stereo and use
> >
> > true Pan Law. I could add a Pan Law selector, seems like it
> > might be useful for various studio acoustics.
> >
> > Then I noticed we use the same formula above to apply 'balance'
> >
> > (using the same pan knob) when sending a stereo signal to
> > a stereo bus.
> >
> > But according to [3] we should be using a true balance control, not those
> >
> > same pan factors above. And according to [1]:
> > "Note that mixers which have stereo input channels controlled by a single
> >
> > pan pot are in fact using the balance control architecture in those
> > channels, not pan control."
> >
> > So I want to change how we mix stereo -> stereo and use true balance.
> >
> > But then I checked some other apps to see what they do.
> > In an unofficial test I noticed that QTractor seems to do the same thing,
> >
> > that is, when pan is adjusted on a stereo track, one meter goes up while
> > the other goes down. RG seems not to have stereo meters and Ardour
> > I couldn't seem to make pan affect the meters, I will try some more.
> >
> > My questions:
> >
> > Is the pan formula above popular?
> >
> > What is the consensus on stereo balance - use a Pan Law, being the
> >
> > formula above or otherwise, or use a true balance?
> >
> > What should I do in the remaining case sending a stereo signal to a mono
> > bus? If I am using a Pan Law as balance, the two signals will have
> > already been>
> > attenuated at pan center so I could simply sum the two channels
> > together.
> >
> > But if instead I use true balance, at center the two signals are 100%.
> > So should I attenuate the signals before summing them to a mono bus?
> > Currently as our pan formula above shows, there would be no attenuation.
>
> you are right - it should attenuate in the middle and gain increase as
> you move. i hate balance controls because you can't move the image
> around the panorama. if you have a stereo piano sample for example, you
> need to move all the "sample data" around the sound stage - not hear an
> amplified L channel and an attenuated R channel which is the balance
> model. Balance is for home stereo's. Pan is for grown ups :)

OK just to be clear I was not implying that the given pan formula
 would be used to do a true 'stereo pan', just that the formula would be used
 to adjust stereo 'balance' giving almost the same results as a true stereo
 balance, but slightly different levels, but not a true 'stereo pan'.

But having said that, yes I'm wondering about a true 'stereo pan' feature.
How would such a feature work?
I imagine that if for example if there is sound exclusively on the L channel,
 and 'stereo pan' is at center then moved all the way to the right, the sound
 that was exclusively on the L channel now moves to the exact center?
That is, all the sound in the stereo field now moves 90 degrees to the right?
It means you'd never be able to completely move an exclusive sound
 which was strictly on L, all the way to the right.

Does that sound correct Geoff?
I can easily implement a true 'stereo pan', given some rules.
Just, now I'd have to give the user the option of using either pan or balance,
 complicating things a wee bit more, but probably nothing an additional
 small pushbutton or two couldn't fix.

Thanks.
Tim.
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Received on Wed Mar 13 00:15:02 2013