<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta content="text/html; charset=UTF-8" http-equiv="Content-Type">
<title></title>
</head>
<body text="#666666" bgcolor="#ffffff">
Hi!<br>
<br>
Sorry for answering this late. And I was wrong in my last mail. The
signal doesn't have to be differentiated but integrated (like you
already did in your first post).?<br>
<br>
The signal in pd represents the current flowing through the
speaker's coil (if we assume it isn't capacitive or inductive load),
producing an acceleration equivalent to the current on the speaker
cone. The peak output voltage of the amplifier is equal for all
frequencies and defines the maximum acceleration the cone can
experience. So we can say the acceleration is<br>
<br>
a(t)= a_max * -sin(w t) // w stands for omega = 2 * pi *
f, a_max is the (peak) amplitude<br>
<br>
If you want to know the speed you have to differentiate it by time:<br>
<br>
v(t) = a_max * 1/w * cos(w t)<br>
<br>
and for its travel:<br>
<br>
x(t) = a_max 1/w² * sin(w t)<br>
<br>
so the cone is moving faster for low frequencies (1/f) and also has
more travel (1/f²).<br>
<br>
It shouldn't be too hard to do this integration with basic pole /
zero objects. A problem using integration only is the lack of
mechanical damping. A real speaker goes back to x=0 if no signal is
present. A simple integrator doesn't - so the 'simulated' cone would
just fly away slowly. So some damping should be included in the
integrator to make it stable. However I'm no expert on designing
filters yet...<br>
<br>
<br>
Looking at power and air pressure - we don't have to care about them
as long as we don't want to include thermal effects or
nonlinearities of the air I think. The pressure directly in front of
the cone is related to the acceleration I think, but I'm not sure
about that. Can anybody confirm that? I think that's not trivial to
answer anyways, because already 10cm farther from the speaker the
pressure and air velocity are different. The power from a 1 kHz sine
and a 2 kHz sine are the same anyways, so why care...<br>
<br>
cheers<br>
Martin<br>
</body>
</html>