Bass traps with angle larger than 90 degrees?

The front wall behind your speakers is the last place to worry about treating, so there's no need to cover that window. However, the rear wall behind you is very important, as are the side-wall reflection points and bass traps in corners. I can't see enough in your photo to tell what you have now or might need. But this short article explains the basics:

Acoustic Basics

Bass traps can straddle corners that aren't 90 degrees. I have an angled ceiling in my living room and I mounted traps straddling the wall-ceiling corners. I'll guess the angle is similar to yours. Look at the center trap at the red chimney over the diffusers, and the traps on either side:



As for spending money on treatment, panels you make or buy can be removed and taken with you when you leave. Just like any other gear such as speakers.

--Ethan