Ideas on building a listening room!!

I spent a few hundred bucks on an acoustical engineer who has done several well known recording sutios in the Bay area. It was some of the best money I spent. On the construction side if you are going to get the most out of the designs you will have to supervise your contractor very carefully. Many od the construction details are not common to residential construction. Don't forget to get an electrician who has built instrumentation labs. Super AC power makes more difference than most imagine.

As an Architect I first say make it beautiful. As an audio buff, I say make it work. It is a issue of whether you design from the inside out or the outside in. Since you say that you have lots of room to build, I take it you are not in on a cramped city lot and do not have to worry about disturbing the neighborhood. If you have a basement in the existing house you will want at least a crawl space below your addition if not a full basement. It will be much easier to run wires and experiment. A slab would give you tighter bass response though. Hard surface is not all bad. Do you want windows? Do you have a view? I personally would look at the orientation that you want and determine how that fits with the existing house. Do you want it to be a retreat of solitude, or a gathering space for all your family? You can always cure a bad sounding room with surface modifications, but you can only plant ivy if it does not look good from the outside!

In general I agree with Wombat but in every construction project that has a utilitarian bent (good sound) there is a tension between aesthetics and engineering. If you spend all that money and get a bad sounding room why bother. Surface modifications cannot make a bad sounding room sound as good as a good sounding room with surface treatments.