Basic Treatment

Hey Guys, first of all, let me say how much I appreciate the information on this site! I am in some sort of dilemma right now, and hope to find some help on here: We are renting a room (6.5x12 meters, ceiling is 2.80m high) for rehaersal and production. An area of 6.5x4.5 meters has been seperated from the rest by a wall, consisting of 2 layers of drywall on each side and filled with 10 cm of rockwool. The other three walls are probably brickwalls with plaster. The room also has a concrete ceiling and the floor is covered with carpet. on the middle of the celing, parallel to the 4.5 meter walls, there is a lintel (I hope thats the correct term) about 30x30 cm of size, which I've been told is maybe not even bad for the acoustics. Now as you all can probably imagine, the sound is really bad in there. I was thinking about putting up basstraps (superchunk method) in all 4 corners, as I read here that you can't have too much bassabsorption. But I'm not sure as to what to do about the reverb and reflections. I've been told to deaden the front of the room up to the lintel, and keep the back live. I've also been told the exact opposite. Can someone point me in the right direction? We try to get this done on a 500-700€ budget. I now I won't be able to work wonders with this, but all I need is a decent environment for production, not a topnotch mixing suite. Thanks in advance an a merry xmas! -Chris Edit: I forgot to add that there is window in the partitioningwall, about 1,2x1,2m. I placed it in a way that you I have my head 38 % from the frontwall when i face the middle of it. also, in the back of the room there is a door in that same wall, so we dond't have to climb through the window ;).

Here's a good link to building bass traps and broadband absorbers. Placement of traps is shown here