[LAD] Mixing audio: Implementing pan and balance
Tim E. Real
termtech at rogers.com
Tue Mar 12 05:23:02 UTC 2013
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 , we should be using a Pan Law ,
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  we should be using a true balance control, not those
same pan factors above. And according to :
"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.
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.
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