The title says it all. I have an NHT sub, currently sitting on fairly dense, high quality wall to wall carpet and pad, underneath of which is concrete. [My home theater is in the lower level of my home.] A friend says the sub is not performing as well as it could since it sits on carpet, and recommended that I cut out the carpet in the form of the sub, and put the sub directly on the concrete. Or, alternatively, at least put a piece of heavy slate on top of the carpet, and the sub on top of that. My sub is not down-firing, the woofer is pointed out the front of the unit. Any other obsessives out there who have gone down this road? If so, what were your results? Thanks.