Eric Kampman erickampman at me.com
Fri Nov 12 04:22:08 UTC 2010

```Hello,

I'm writing a synth module on top of jack and I'm starting to contemplate stereo.

I looked up "pan law" and understand that center should be -3 db (or some say -3.5 or 4.5, whatever) given unity at panned hard L or R. It was said that in an ideal room I should be down -6 db in the center.  That would mean linearly transitioning from unity gain to completely off as one pans, I *think* (-6 db in the center = .5).

So that's one (very easy) way to go...

There was also mention of "equal power". Since power is proportional to signal squared, this means with parametrized L and R functions

L(t)^^2 + R(t)^^2 = 1,    0 <= t <= 1

We need an f(t) such that f(t) = L(t) and f(1-t) = R(t).

I played around this for awhile and using the sum of the square of sin and cos etc I got an f(t) of

f(t) = cos( pi * t / 2 )        (details available on request)

So L(t) = cos(t * pi / 2) and R(t) = cos((1 - t) * pi / 2)

And that seems to work out correctly.

Is this equal power version worth spending the processing cycles on? I intend to make pan envelope and LFO controllable so it's not going to be the case that the pan value can be thought of as relatively static.

Thoughts?
Thanks
Eric

PS now that I know what I'm looking for web search turned up this:
http://www.midi.org/techspecs/rp36.php

```