[Rokus666]

Thank god I have cement sealing and floor with tiles.

And pretty fortunate to have a double sheetrock wall with a kitchen behind front end. That should contribute bass absorption I think.

Maybe I should put some fluffy fiberglass in the corners and staple it firm.
I was affraid that I would dead the room with too much panels laying around.

Right now I have 5 pieces of 705 4" thick
4 pieces of 703 2" thick

I have red that i need to build the diffusor based on some formula.
Right now I have guitars and a bookshelves on the back wall and that functions same as factory built diffusor. So I think it should be good for now, definitely better than before...

Well, when I buy my house, I will definitely have someone design my studio from the ground up. There is a lot of higly skilled proffesionals on this forum, and I wouldn't want to be the one doing all this building and calculations. Need to focus on music and musical ideas first.