[Doug McDonald]

wrote:


Where it DOES have factor is like this: suppose you want
to design a subwoofer with a small volume. Indeed, the
acoustic compliance of such a volume is small. You find
that when you put a high-efficiency woofer with a litght-
weight cone in it, the resulting system resonance is too
high to be a "sub"woofer. So, you add mass to the cone.
This does three things:

1. Lowers the resonant frequency of the system,

2. raises the Qt of the system,

3. lowers the system efficiency.

So, yes, the small, closed box system has a lower efficiency
for a given bandpass, but NOT because the air is stiff, it's
because the moving mass of the cone has to be high to
get the resonant frequency down there.


I've wondered what would happen if you left the mass alone and
simply boosted the bass signal so you get the same speaker movement.
Does this screw up relative phase? If so, what happens if you
use a digital filter before the power amp so as to fix that up?

Would the low bass efficiency be the same as if you had
weighted the cone?

Doug McDonald