I have built floor risers on and above concrete floors. You don't want to leave the cavity hollow but fill with rock and then vent or port the riser. This method diffuses and breaks up standing waves that tend to travel along large flat surfaces. You have to step up into a room such as this via a step or two . The other way that has worked well for myself would be to put down a vapor barrier and then jute fiber pad with a real or high content wool fiber. Natural fibers sound better even underneath a wool rug. The wool seems as if its more of a comb filter and the resulting highs are better and more linear and extended. Foam under man made fibers has more bounce and seems to have more of a resonant peak. That's been my experience. Tom
Hardwood floors in basement music room?
I currently have carpet over concrete, and I'm thinking about removing the carpet and installing engineered hardwood over a glued down underlayment, does anyone have any pro or cons on this. The underlayment I was going to use is a lumber liquidator product called Eco silent sound HD, they also have a cork underlayment .