Box volume

[danrowland]

Can someone explain how to calculate the box volume with multiple drivers such as in a 3-way system? Also just how important is the box volume? I want to install a Vifa PL18 into a closed 20 liter box but the driver Vb is about 10 liters. Will it matter that much? Can I compensate with the crossover or something?

[bking]

> Can someone explain how to calculate the box
> volume with multiple drivers such as in a
> 3-way system? Also just how important is the
> box volume? I want to install a Vifa PL18
> into a closed 20 liter box but the driver Vb
> is about 10 liters. Will it matter that
> much? Can I compensate with the crossover or
> something?

Dan,

The box volume is dictated by the woofer parameters. You'll need to account for any sub-enclosures for the mid-range if you need one.
I did some calculations via WinISD (quick, but not I'd bet the farm on 'em dead-on accurate) and came up with the following:

Vb= 20L
Closed f3=89Hz
Qtc.= .51

Vb= 14.2L
Closed- f3= 85 Hz, Qtc.= .56
Ported with 2" x 6.25" vent, Fb= 46 Hz

In view of the above, I'd use a ported box rather than sealed unless you are going to use a sub crossed over second order at about 80Hz.