[Don_S]

Has anybody used these? I already have five 2'x4' acoustic absorbers in my room but I would like something for the wall behind me. There is a large window there so I only have a little wall left to treat on either side. I am trying to avoid 6" deep monsters.

https://www.amazon.com/gp/product/B07LH6NBGF/ref=ask_ql_qh_dp_hza?th=1

[Big Red Machine]

Those are slotted panels over foam. Limited frequency effect. Probably more diffusion than absorption with these.

Why not a deep curtain rod arm and a rod that extends 2 feet either side of the window and hook them over the rod in front of the window when listening? Go for the 4 inch at least using 703. Bite the bullet and go big Don! Hell, I love spending other people's money - make them art panels to boot!!

[DannyBadorine]

Has anybody used these? I already have five 2'x4' acoustic absorbers in my room but I would like something for the wall behind me. There is a large window there so I only have a little wall left to treat on either side. I am trying to avoid 6" deep monsters.

https://www.amazon.com/gp/product/B07LH6NBGF/ref=ask_ql_qh_dp_hza?th=1

I haven't tried those but I agree with the first comment that they will probably diffuse more than absorb.  But what exactly are you looking for?  Is your room too alive?  Diffusion is often used more than absorption behind the listener so maybe these panels are what you want.  They are thin so it's unlikely that they will work on any frequencies below 1KHz.

[JLM]

Diffusion is based on depth of panels.  7.5 inch depth is limited down to 1100 Hz, thinner will be limited to higher frequencies.  Design shown provides very little opportunity for absorption.  Sorry laws of physics apply here.

I use 10 GIK 244 2ft x 4ft panels (found here at Audio Circle) in my 8ft x 13ft x 21ft room.  2 full range version on the front and back walls, 1 on each side wall.  4 bass trap versions straddling the front corners.  These are absorption panels.  Note that I also have 3 tall bookcases on the side walls used as "casual" diffusers.  Not all absorption panels are created equal.  Check the specifications (most don't even have them).  IMO GIK knows what they're doing.  These panels are highly effective.  My six full range panels made a tremendous difference in a restaurant that had huge reverb issues and a significant difference in a friend's rather awkward room, frankly the 10 panels I own make less of an improvement in my "ideal" room but was more of an audiophile mania move.