Drywall basstraps?-Ketchup stained handdrawing included

Hello I am in the process of converting a small bedroom into a studio. This is a an apartment in a block, so high sound levels are out of question. So no real sound proofing issues here. What I mainly want to achieve is a good sound for playing, mixing and home mastering (well, yes :oops: )...it's mainly a hobby. Ok, so the room is about 2,7x3,4x2,2 meters (about the size of a detergent box). It has a window in front, and a door on the back wall. The back wall will have a little hole through wich cables will go to the computer sitting in the dresser behind. The room is built of concrete walls (left, right and front) and thick calcarous stuff (don't know the name really...not drywall...alot thicker, about 15 cm) the back wall. I have lined the walls with drywall, seated on metal studs, puting regular yellow mineral wool under the drywall (about 5 cm thick). I have done this in order to dampen a bit the sound transmission, and in hopes that it will act as a bass absorber too. The concrete walls were extremelly uneven so the drywall was necesarry...so no missplaced investment here. Now I am thinking about using 3 drywall pieces (1,2 and 3 in the drawing) to close all the three corners in the front (left, right and ceiling). Behind those I would fill with mineral wool. Besides helping a bit with the sound spreading and avoiding the buildup of bass in those corners, do you think those 3 formations will also act as bass traps given the fact that they are totally sealed? What if I drill some holes in them (5-10 cm in diameter?) 1 and 2 will not be used to soffit mount speakers, I will use speaker stands. Thank you...i hope I covered all the aspects in order to make myself understood.

I would really appreciate a little bit of input, since my workings are advancing, heh....soon I will have to decide what to do... Thank you P.S. Budget is not really an issue....we are talking about a few drywall sheets.... :)

I suppose the drywall should be at least perforated (over 15-20%) to cover a porous corner absorber... but the regular practice is to cover the mineral wool with acoustic transparent fabric or wood strips. You will need good absoption on the back wall too.

It doesn't need to be preforated.... Yes, your idea will work...the only downside is that it will not be tuned to a specific frequency. The rock wool will help damp out the resonance, broadening the Q of this trap. Be careful not to make the drywall panel too stiff, or it won't be effective at low frequencies. On the other hand, if it's not well supported it will be fragile...and might have a resonant frequency below the range of interest. Cheers Kris