I first got the diffuser panels for the living room to help with soundproofing. I still wasn't able to contain the sound as the walls are thin in my old house. So I moved location to the basement.
This room is much more lively than previous room. I could lower the volume level approx. 5 db while still being perceived as loud as living room. With more detail and clarity.
I listened without the panels for about a month, so that I could tell what affect they were having when I placed them in the room. They seemed to add a still quietness to an already quiet room. Marginally focusing the sound, revealing more detail/clarity in music.
The photo above is an updated speaker arrangement.
The rear center speaker facing the wall makes vocals sound fuller. The Studio 100's and the B&W 601's on the shelf, are the front mains. There location makes for a wide solid front center soundstage. The B&W's are critical in this location for adding to the width of the center channel as well as complimenting the Studio 100's in presenting a cohesive image. The monitor 9's in the corner of the room, add width to the overall soundstage making for a more natural presentation in MC stereo, compared to just 2-channel. Which can be done with just the Studio 100's. The other two bookshelf speakers located above the Studio 100's. aren't really needed ,except for the YPAO on my Yamaha to work, they add fill.
Listening mostly in MC stereo, bass is distributed more evenly than with 2-channel stereo. 2-channel stereo by itself is good, but I prefer the wide soundstage of MC stereo. With MC recordings such as sacd or dts, the soundstage it's far superior to 2-channel stereo in this room.