The fact that the back wall is only ~1/3 to 1/2 high relative to ceiling, I would think that room modes developed due to the front to back distance, would not be that much of an issue. I would try some DIY treatments to test the value of purchasing treatments.
Back wall treatment?
I have a small room which I’ve treated with bass trap in the corners and absoprtion panels at 1st reflection points on the front wall, side walls and ceiling. I am quite happy with the results. I am considering what to do with my back wall. Due to the size of the room I have to sit with my back essentially right up against this back wall. The wall only goes up to about ear level, above that its open to my family room and kitchen.
So my question is what do you suggest for this short back wall? Broadband absorption with something like the GIK 244 panel or diffusion or nothing at all?
So my question is what do you suggest for this short back wall? Broadband absorption with something like the GIK 244 panel or diffusion or nothing at all?