well i wasnt planning on putting up a back wall (I dont know why there is a grey line in that diagram). We wanted to keep the room kind of open in design. i know this isnt the best for isolation but there is only one other person in my band (we write and record every instrument), and with such a small space that we have we didnt we to lose anything by building walls, and be able to easily communicate while tracking. I know that i said the room is 9x9 and thats terrible for bass frequencies but does it help that there is no back wall?