I've considered to add some diffusers on my absorbent drop ceiling and some RPG Bad panels (or somthing similar) on sidewalls closest to the listening position. The reason is because I would like to get some more liveliness and it would also be good to cover the frame of the drop ceiling which are causing some reflections.
If I do this, it will be in the area of early arrival sound, within 10 ms. And many are saying that it's better to use absorbents for early reflections and rather add more dffusion for later reflections, typically after 20 ms.
Another thing I'm uncertain about is if using diffusers in a narrow place like this (on drop ceiling and sidewalls), will cause unwanted specular reflections.
I've attached some pictures and the lines on the drop ceiling are the places I've thought using diffusers. The pictures are somewhat outdated. I've removed the diffuser on the frontwall, using less absorption on sidewalls and started to make some changes on the slanting ceiling now, but they still give a good impression.
I use diffusion only on the backwall today. The absorbents you see behind the speakers and on the slanting ceiling behind speakers are covered with a reflective membrane of mids and highs. An exception is the superchunks in the cornes that absorp all the way up.
Would be great with some input concerning adding diffusion. Will using diffusion in those areas cause specular reflections? Am I better off adding diffusion on the frontwall in front of basstraps?