To address the question of ’ sound quality - benefit ’ and with a focus on the ceiling.
The ceiling and the wall behind the speakers will be the two most important areas to focus on.
Since the ceiling height is relatively good already and adding treatment will be easier.
There already you have some analysis ...
My listening space ceiling height increases from system placement at the lower height and the highest at the opposite end.
I can easily hear the difference in decay time from one end of the room to opposite end ( lower decay time at the higher ceiling position ).
Absorption above and behind the speakers should help level out the whole room decay plot.
Diffusion in a listening room is more beneficial for a natural sense of ambiance ( balance ).
More analysis and some opinion ...
If you want a sense of what room interactions are then play some test tones ( 500 Hz / 1000 Hz ) and walk around the room and listen.
You will notice phase anomalies everywhere!
If you are up for more introspect and a very different approach to acoustic treatment then I suggest looking into Hsu Research.
DHDI: Delta H Design | Hanson Hsu
Delta H Design | Quantum Acoustics™
Please note that I am not associated with the Research Group and am not making a recommendation for services.
