On Thu, 3 Nov 2005 01:58:39 -0500, "Michael Kennedy"
wrote:


Correct me if I'm wrong, but wouldn't a higher density material cause the
damping to improve? (Lead speakers anyone?)

or depleted uranium : )

I'm not sure exactly what you mean by dampening but will have a go at
explaining why dampening materials are of benefit in box building.
In regards to dampening in box material itself( mdf, plywood, concrete
etc...) Yes the more rigid and dense the material the better as it
acts to reflect the back waves better resulting is less energy loss
and of course lower resonance which only adds coloration/noise.
In box stuffing the idea is to add a material such as polyfill which
acts as an "acoustic maze" or baffle which has the effect of
increasing box volume. There are special materials such as
acoustastuff which has the optimum characteristics, they can be had at
parts express or any good speaker parts dealer.
In the old days we used a material called kimsul, a kind of wool-like
material which has been rendered obsolete by better materials

As for box materials, I've seen them made with just about every kind
of high density material.
I've always favored acoustic plywood.( 10 ply birch or white oak,
usually 1-1/4 inch thick. It has the advantage of being a bit denser
than regular plywood as it's pressed under greater pressure and with a
glue that has stronger adhesion qualities than the water based stuff
used in ordinary ply.)
The best box I've seen in regards to it's dampening properties was
formed out of concrete. Hard to build, heavy as hell and not too
attactive in the home setting though.
Years back a friend of mine had me help him wire up an isobarik that
he'd made using 8 inch concrete drain pipe. About 4 feet tall as I
recall using two woofers wired out of phase for push/pull effect.
The bass was fairly clean and it had decent efficiency specs but were
they heavy! Not too pretty either.(though he did improve their looks
with some concrete paint and a bit of gloss laquer.)

I've had occasion to use the mdf especially designed for audio
boxes.(can be gotten at most automotive sound shops)
It's of a finer construct material and is sealed on the outer surfaces
rather than the more coarse, open grain stuff you get at home building
supply stores. It's also thicker( 7/8 for what we used) and is easier
to apply paints or finishing coats to.

I talked to a fellow online that was attempting to use wonderboard to
build a set of boxes, though I never heard how it worked out.