Front or Back wall diffusers

As a general rule I like absorption right behind the MLP on the back wall and diffusors to the L and R of the absorption. Try front wall first.

@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

This is my back wall, I have absorption panels just below my on wall slim subwoofer. To the right you can see the Auralex Pyramid Sustain diffusors which are back filled with polyfill so they double as bass traps. It doesn’t have to be either or. In this pic you can’t see the treatments to the left of the sub but it alternates, absorbers to the left of the sub, then diffusors, then absorbers, etc.

if your sitting position is cleared roughly 1/3 of the room from the back wall, the treatment behind is less critical. 

Do you know how long bass waves are? You must be referring to a castle.

If we are talking front wall I would say floor to ceiling bass traps in the corners are first step. If we are talking back wall I would say absorption behind MLP is first step. Then you can experiment with diffusion. 

One thing that hasn’t been brought up is measurements, if you measure it helps confirm your choices. You don’t have to get "technical" to measure. I got a PW Link preamp from paradigm with ARC room correctionfor$199. I use the digital out from the Link into my dac, and presto, check out the before and after. The before graph is already pretty tight because of my room treatments, ARC just dialed in for that last bit of OTT clarity:

@seanheis1 

Can you please post pics of your own setup as an example of your general rules? Thanks