[sdiy] Panning (again)

[Neil Johnson]

Someone a while back posted a link to a post by Graham Hinton on
MuffWiggler with some relevant information:
https://www.muffwiggler.com/forum/viewtopic.php?p=1674967#p1674967

I'll copy the pertinent text here for those who don't frequent MW:

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The proper professional stereo pan law was defined by the BBC way back
in the 1930s from empirical research and is neither -3dB in the centre
(so called equal power) nor -6dB (linear crossfade). Mixer designers
have heated arguments about whether it is actually -4dB or -4.5dB in
the centre, but more important is the shape of the curve towards the
extreme attenuation side.

Stereo panning is an illusion based on a loudness balance whereas the
brain decides the panoramic position of a sound from the delay between
arriving at the ears. That is why panning on headphones goes over the
top of your head rather than around the front--the differential delay
of panpots is always zero. To get a law that feels right when turning
the knob and doesn't rush across the middle you need the BBC law. The
balance is very delicate and a 0.5dB error can produce a 25% position
shift. I know this because I designed the Solid State Logic
Programmable (read VC) Panpots for the BBC in the 80s. I also designed
their Programmable Surround Joysticks for a Lucasfilm console and the
laws for that are equally non-obvious.

It is easy to replicate the BBC's method, all you have to do is
balance a left and right channel volume and measure the level
difference for apparent position. It is easy to do and check, but
people keep repeating the same misinformation without thinking.

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Neil