aschuh
I do not think this is physically possible. Estimating the speaker weighs 50lbs and the cone and voice coil 8 ounces, the speaker cabinet would move 1/100th as far as the cone, for an equal and opposite reaction, assuming 100% of the energy moves the speaker. The cabinet is larger in surface area, but 3db is a 50% loss in acoustic power. This is not possible.
Specifically, I measured a 12" Rhythmik sub, front firing, at minus 3 - 4 dB, when sitting on Nobsound springs (compared to standard hard rubber footers), which obviously allow for horizontal movement.
The loss in bass energy was quite audible.
I do not think this is physically possible. Estimating the speaker weighs 50lbs and the cone and voice coil 8 ounces, the speaker cabinet would move 1/100th as far as the cone, for an equal and opposite reaction, assuming 100% of the energy moves the speaker. The cabinet is larger in surface area, but 3db is a 50% loss in acoustic power. This is not possible.