If all you can do is the wall behind you then do that.
If the wall behind you is close, like immediately behind your listening position go with 100% absorption and as much as you can.
If it’s 6’ or more away, a mix of absorption and diffusion.
Another thing to do is consider speakers with more controlled dispersion. Klipsch Heresy’s for instance, line or ESLs are going to be better for you, as would open baffle.
If you can do the left wall, along with thick curtains on the right then do that too.
Keep in mind a lot of room treatment looks really good now, GIK art panels for instance let you pick any art at all.
If the wall behind you is close, like immediately behind your listening position go with 100% absorption and as much as you can.
If it’s 6’ or more away, a mix of absorption and diffusion.
Another thing to do is consider speakers with more controlled dispersion. Klipsch Heresy’s for instance, line or ESLs are going to be better for you, as would open baffle.
If you can do the left wall, along with thick curtains on the right then do that too.
Keep in mind a lot of room treatment looks really good now, GIK art panels for instance let you pick any art at all.