Re: [LAU] studio prep question.

I am in a similliar situation and do I believe in

A - decoupling
B - mass

Of course, best would be to build a "room in room".

I will try to decouple the speakers in this way:
http://www.nubert-forum.de/nuforum/viewtopic.php?f=6&t=27261

granite with foam, rubber and carpet

 

And I do believe that sand is a really smart material for this purpose:
A pillar filled with sand as speaker stand. The speaker could sit on top of one meter sand.

And building a second wall filled with sand?
This requires some calculation regarding structural analysis:
How much mass does the floor carry? How thick could the wall be?

Sand is cheap, heavy and moves e.g. works.
It is absorbing powerful sound waves with mass and friction. 
And it can be portioned in the build process.