12 Mar
2013
12 Mar
'13
10:56 a.m.
On Tue, Mar 12, 2013 at 01:23:02AM -0400, Tim E. Real wrote:
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.
6 dB actually.
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.
There are two independent issues involved here:
1. The attenuation at the center w.r.t. to extreme L and R.
2. Whether the center or the extremes should be 0 dB.
(2) is very much a matter of taste and of virtually no practical
consequence : you will adjust the fader (channel gain) to get
the right balance anyway.
Regarding (1), if you take psycho-acoustics into account you'd
want -6 dB at the center for low frequencies and -3 dB for high
frequencies, with a gentle crossover at around 500 Hz or so.
So the SSL compromise of -4.5 dB makes sense.
Note that unless you use the panner to move a sound around
during a mix, all of this hardly matters: you will adjust
the balance anyway and compensate for whatever the panner
is doing.
Returning to (2): for a panner (mono -> stereo) I'd prefer
0 dB at L and R. For a balance control (stereo -> stereo)
I'd prefer 0 dB at the center position.
--
FA
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