Front or Back wall diffusers

@avl1947 

I use Anthony Grimani's acoutic recipe and have pics posted in my profile, see the diagram below. He uses combo panels on the front wall and you can see how he stagers treatment on the backwall:

Example of a combo panel:

https://www.amazon.com/Absorption-Diffuse-Acoustic-«Pulsar»-rec-studio-laminated/dp/B07LFKTJB6/ref=sr_1_26?crid=2N19LG1S1XJ00&keywords=diffuser+acoustic&qid=1689370084&sprefix=diffuser+acoustic%2Caps%2C242&sr=8-26&ufe=app_do%3Aamzn1.fos.f5122f16-c3e8-4386-bf32-63e904010ad0

Talk to GIK.  They’ll give you some good advice given your room and offer products that are relatively reasonably priced. 

It is recommended that the wall behind the speakers be reflective in nature, so that the sound develops properly. On the contrary, the wall located behind the listening position should be absorptive, so that the rear reflection of the sound does not interfere with the perception of the stereophonic image.

 

Weird how you seem to answer your own question.

@avl1947  I agree with you. Absorbion behind the listening position. I'll add that the corners of the front and side walls will often need bass traps or absorbion panels. This not only controls bass, but helps create and shape the soundstage

Without more info, you only will receive useless advice. Need to know speaker position, listening position, etc.