Originally Posted by krabapple
Well, I wonder if reducing vibrations in large room objects, including walls and floors, would perhaps 'tighten up' the sound significantly all by itself...requiring no 'trapping' role for the space beneath the device.
Oh, I find it hard to believe that the small space underneath the platform has any function as a trap. Doesn't it have to be some fraction (e.g. 1/4) of the wavelength of the influenced frequency? A 3' platform would have no effect on anything below about 115 Hz.
As I said, the 'tightening' effect has been reported in spaces where structural resonance wasn't an issue, e.g. all-concrete rooms. I rather suspect that it has something to do with the support of the subwoofer case, affecting the way the case moves in relation to the cone. There should, then, be a difference between down- and side-firing designs. But I haven't noticed any pattern in the reports. (Mine are down-firing.)