New control room project in Finland, design help?

Hello! This is my first post after about an year of just reading. Situation is this. I've rented a small space from an industrial building for a Control room and booth for vocals,amps etc. I'm going to do mostly guitar/bass, vocal overdubs and mixing. Location is great, the building is great but my space is quite challenging. Basic measurements are L 8,6m (28.2'), W 2,55m ( 8.3') and H 3,15m (10.3') So it's long and narrow. Both long walls, end wall, floor and ceiling are concrete. Big and sturdy. One of the long walls is outside wall with windows bricked in and thus leaving me 0,3m (0.98') deep "windows" in there. The walls with the doors are 2x4 frame with double drywall. I don't have to deal with neighbors so isolation is not vital, only acoustics. I've played around with room mode calculators and figured I'd split the length in to a CR and a booth. So the way to CR would be thru the booth. I've thought of going for a L 5m (16.4'), W 2,55m (8.3'), H 3,15m (10.3'). This seems good for the modes, and then do treatment up from there. What should I do for acoustic treatment? As cheap and DIY as possible of course :D I think speaker soffits are out of the question because I use Genelec 8020 nearfields and 7050 sub. Do you think the "windows" should be first evened out with insulation/drywall and then start thinking about absorption, Helmholz slats and the like? Here's a picture and the sketchup file for what I have now. Sorry, skp is a bit crude. This is my first pass at this. Thank you already.

Oskar, It's pretty narrow, bro! :wink: You could split it up into two rooms, but you may be better off with a one room studio and focus on treating 'areas'. You don't need to 'smooth' out the blocked in windows, they are fine and will probably add some dispersion. Be sure to trap well and don't forget the ceiling/wall corners up above. This is a good place for trapping. Start with vertical corners trapping, set up your mix position at one end, absorption panels at early reflection points, ceiling cloud, and then get REW or FuzzMeasure and test the room. Then go from there. BTW, Helmholtz resonators are a last resort... do broadband trapping first. I doubt that you will need them. Rome wasn't built in a day and things evolve. Take your time and no short cuts. Cheers, John