Thread: Pink foam for a speaker box?

Hrmm. You're right in that the box determines sound. But I highly doubt the foam is doing much. There's an equation that represents the type of foam vs. thickness and it helps calculate to what frequency the foam is able to absorb frequencies. The truth is that there really isn't anything large enough for the wave lengths in the sub bass region.

So why do people add foam n' such? A couple of reasons...help remove resonance(ringing), mimick air space when not enough is available, and to help with second and third order harmonic distortion.

So now back to your question, is it dense enough to make quality sound? Well if you were using the foam as a skeleton for the fiberglass the real question is if your fiberglass is thick enough?

Fiberglass Thickness Layers for Car Audio

So your foam isn't an issue Hope that helps!