Advice on dedicated room

I would not add a wall reducing the limited space you have. It is entirely possible to treat the room and have superb acoustical performance, even if the room is a perfect cube. The idea of building a new wall to provide non parallel walls I would also dismiss. Having a changing dimension will not remove problematic nodes, just change them for different ones that still need taming.

You have what can be considered a small room and as such needs absorption more than dispersion. Absorption must take the form of broad-band construction to be effective. The often recommended: 'just add a rug/curtain/bookcase etc. are only narrow-band absorbers and although they are better than nothing they will not reduce the decay sufficiently across a broad range of frequencies. You mentioned putting a 45 degree angle on 2 corners: that is where you could/should fit bass traps which will greatly improve the room's performance below the Schroeder Frequency. Strongly recommended.


A suggestion is to buy a microphone and use the excellent free download REW and measure your room. This will take the guesswork out and provide solid evidence of what any added treatment is doing and also help find the optimum place for any sub/s.

@lemonhaze, I disagree. I think it is better to make the room as good as possible, and then treat it. But then, my crystal ball has been busted for some time now.

Hey Terry, I don't disagree with you disagreeing but in his smallish room it's the lesser of two evils. It was a popular consideration for awhile but lost momentum. I unfortunately lost a lot of links and papers when my computer died, I would like to have provided plots of a room where they were taken with zero treatment, then with increasing treatment and the same room with the roof sloping, done as part of a dissertation. Essentially the results were close just with some of the treatments in slightly different locations. So the way I see it, why go to the considerable expense and bother for very little if any gain.

Strength is not an issue using 2x4 framing. What is an issue is isolation and vibration control. Using a 2x6 framing allows you to stagger your vertical studs so the sheetrock on each side of the wall is independent from one another.  You are almost as good as 2 2x4 walls.  
Lay the first layer of 1/2" sheetrock vertically or horizontally.  Then use an adhesive to add 1/8" of polystyrene to the whole wall & ceiling.  Finish with a second layer of 1/2" sheetrock the opposite direction of the first layer.
The walls & ceiling will have zero vibration and great isolation. 
Fill the empty wall cavities with insulation ..of course. This really works.