Timber floors for HT room

[David Meek]

I'd fill the voids completely with a clean, dry commercially available sand. Don't go out with a shovel and collect your own.

[aud19]

I'd wager you'll want to fill the gap with something preferably absorbing. Otherwise you're basically making a drum. Not good for acoustics.

As for the floor, yes it will make the room brighter, more reflective, lively etc. You could consider using something like cork flooring which is a compromise with hardwood appearance but still offers some sound absorption. Otherwise yes, you will also need acoustic treatments and likely something like a throw rug particularly at the first reflection point on the floor. Taming the first reflections on the walls and ceiling will also help tame the room as well.

[Linmuse]

I'm in the process of fitting out a 7.5m x 4.5m x 2.9m (24.75'x14.85'x9.75') room for HT.
The floor will be 19mm(3/4") solid timber boards on timber batons. The batons are fixed to a concrete slab and there's a 80mm(3") air gap between floor boards and slab.
My question is: Is there any benefit accoustically in filling the air gap with sound absorbing insulation to limit any echo or will it be better leaving the gap empty? Will money be better spent on other room treatments?
Im concerned the timber floor may make the room too reflective.
I like to play music and movies loud, should I be isolating my equipment from the floor to minimize vibration?
Equipment used; Rotel 1098 pre/pro
Sony DVP NS700P dvd
Adcom GCD 700 cd
Adcom GFA 555II amp
Adcom GFA 2535 amp
B&W 803D front
B&W HTM2D centre
B&W 580 rear
Velodyne DD15 sub