The room within a room seems it might be excessive for domestic systems. That may be more justified for recording/monitoring room designs.
A less expensive option might be utilizing 2x4 studs on 2x6 sill plates. Then stagger the studs so every other one contacts an opposite wall (while maintaining 16" spacing).
Not sure I agree with the double drywall either. Yes that may "tighten" the wall and ceiling surfaces but will it be too "dry" sounding?
Lastly, from Jim Smith's book, he recommends installing 2x4s on their side on top of a concrete slab, then overlaying wood floor on that.
A certain amount of flex can support a constructive balance in a room.
A less expensive option might be utilizing 2x4 studs on 2x6 sill plates. Then stagger the studs so every other one contacts an opposite wall (while maintaining 16" spacing).
Not sure I agree with the double drywall either. Yes that may "tighten" the wall and ceiling surfaces but will it be too "dry" sounding?
Lastly, from Jim Smith's book, he recommends installing 2x4s on their side on top of a concrete slab, then overlaying wood floor on that.
A certain amount of flex can support a constructive balance in a room.