music room design questions dimensions/flooring

I guess much has been written previously, yet I still seek answers to the following:

* for a room with dimensions of 13'1"(4.00m) width x8'8"(2.65m) height, what would the "best" length be? Is 24'6"(7.45m) too long? I can shorten length if required.

* for wooden floor(hard wood bearers/joists and 1" sheet floor), should floor be fixed directly to subfloor or should it be "decoupled" via rubber or other spacer? ie. does decoupling improve sonics?

I am hoping to avoid the theory and get straight to the definitive answers.I am all theoried out at this stage and want to finish modifying my music room.
Maybe this will give you some insite. try using the Golden Ratio method. I have played this this with success. 16' x 26' x 10' is a nice size but you can do some math with what you have and get close. Decoupling the floor will remove vibrations from other places in the house. Rubber spacers are used in some recording studios. Check out the forums on if you want more detail.

The simple answer is it isn't simple experimentation trumps theory in my view.

In theory, ideal is;

1:1.6 :2.33

which suggests you should make your room 6.2 Meters long and if you placed large acoustic panels (such as Realtraps, GIK etc.) on the ceiling to bring ceiling down 20 cm you may get the ideal dimension.

Decoupling is good up to a point as it helps keeps the noise down for neighbouring rooms. However, you really want sound energy to dissipate and not remain trapped reverbing in your too much decoupling may actually be bad (imagine the floor floating like the membrane of a drum = very bad). Absorption or damping is just as important as decoupling....heavy damped rubbery material between floor and joists with lots of glue to make sure nothing is loose.

In practice, theory never works and you should probably consider seeking advice from an expert who has doen many installs and has learned first hand what does and does not work.
A local HT design office suggested to add another plywood layer to the first layer over roofing felt and screwed into the first layer, but not the joists. I did this when building my home and am pleased with the result.

Check out Steve Deckert's Optimal Dimensions for a Listening Room whose measurements came from the Masters Handbook on Acoustics. Shadorne's equation is Option C (the option I am planning to use when I remodel). Also look at Steve's other papers on room treatment while you are there. It always helps when someone has already gone through the motions and relays their experiences.

Also do a forum search on "room treatment". There is plenty of information available. Stick with the research (you can glean fact from fiction) and you will have a better chance of getting it close to right the first time. IME