It´s in our basement and has the following measurements 2.35m x 4,38m x 5,48m(HxWxD).

The front speakers and the screen will be on the short wall (4,38m) and the listening position will be in the middle of the room.

3 of the walls are outer walls and made of bricks and concrete, when knocked on, they sound very dead.
But the fourth wall is a concrete wall seperating this room and the washing room, when knocked on it has kind of a "booong" sound.

I´ve thought of screwing some wood to the wall, then put some 50mm rockwool in between them, and finish it of with some plasterboard.

Is this a good idea ?

The floor and ceiling is concrete too, the floor will have a thick carpet.

What would you recommend for room treatment ?

Regards
Kim