Room treatments are tough. Here are few random notes:
I'd recommend you identify a specific issue before trying to solve the 'problem'.
As a rule of thumb: A very good room will have about 20% of all surfaces covered with broad band absorption and 20% of all surfaces with broadband diffusion -- plus bass traps in corners. and by all surfaces, I mean walls, floor and ceiling.
Treating only a small area of a room is kind of like throwing a bucket of water on a house fire. Try opening a window and seeing if there is a difference -- a window is a perfect absorber; as any sound that hits it does not reflect back into the room. My point being that, the small relative surface area likely does very little to the overall sound in your listening space...
Be careful when using thin absorption. You can reduce a specific high frequency reflections that accentuate other frequency -- either positively or negatively.