don't believe me? - put a heavy dumbbell on your acoustics - the sound will deteriorate - it will become jammed ...However, just like isolation produces a decolouration by helping to limit cabinet resonances, placing a tuned mass damper with absorbtion materials atop of the cabinet will realise equally a significant increase in performance.
@serjio - I know you didn't mean speaker cabinets, and your discussion has merit, I am just trying to point out one exception.
Tuned Mass Damper, some of you might want to look that up, those of you holding onto rigid methodologies. You can be stuck in the methods of the past, but once you have tasted superior engineering practices, make no mistake, you will go to church (so to speak).
@pengun & clearthinker - boing boing sounds abso-flaming-lutely glorious!