Quote Originally Posted by Reid Malenfant View Post
Sand is superb stuff for damping any resonances, because each partical can't really pass it on to it's neighbour any nasties are soon damped out.

Wharfedale (an old speaker manufacturer from the UK) used to make a sand filled baffle speaker, the same thing applies, the baffle was non resonant due to the sand filling

Try punching a bucket of sand & see how much it resonates
I guess it has to be white sand with lead shot to avoid colouration of the non resonance.

Still not convinced from previous messing around that lead shot adds anything (other than mass) to the behaviour, and in a resonating cabinet, particle separation and migration would be rapid. In a tubular metallic frame, such dampening would exhibit the same migration which could possibly cause localised ringing, only to be dampened by the sand.
Drop lead shot and sand mix onto a steel plate and listen for the sand hitting it or vibrate the mix in a glass to see the effect....
Even the best graded quartz sand will settle out leaving a fine dust on the top layer as it is effectively a range of particle sizes of unequal mass.

Pretty sure I came across a fairly recent design using the exact same sand technique for dual walls in a DIY speaker array, and yer another for a sub-bass. Also came across a turntable base that was so designed, which seemed a little extreme.