Room treatment is necessary, and I know it equals the sum of its individual components.   Acoustics are not as atrocious as they look. One side is open to the kitchen and the hallway. It's not the ideal room setup. But the upside is that there is no neighbor on that side of the house and no one in the back for 300 feet. With double-pain windows, I have no limit to how loud I want to play. The limiting factor is the eardrums.