I use Rockwool @ 35Kg per M3 floor to ceiling in height as a Absorption Room Corner conditioners. Directly behind and spanning between the Speakers I use a Diffusion Panel.
Each Side Wall has a diffusion pane.
The Rear Wall has a Aborption and Diffusion Panel set at a height of the listeners ears.
The sound is managed in a manner that has improved attraction with these measures in place.
Would it be identified as a accurate treatment using tools the can measure room modes is an unknown for me.