Absorption, Diffusion or a combination of it all?

@kota1  I'll check out their site-thanks.  Interesting that acoustic lens over the window--is that the squarish thing that seems to be hung over vertical blinds?  If so, can't help but wonder if the verticals all by themselves could have acted as an "acoustic lens" similar to the way i played with the blinds on the window behind my speakers.  Have you ever removed it and heard the difference ? 

Although i only spent a few hours on room treatments i will admit that i started down the rabbit hole by reading Jim Smith's book,  "Get Better Sound" and then booked an hourlong phone session with him b/c i had several questions on material in the book as well as idiosyncrasies in my room with doors--he was quite helpful but also urged me not to obsess beyond dealing with a few important things pertaining to my room.

@kota1 -- thanks for the video--i only watched starting at :49 but it seemed to me the discussion was more pertinent to home theater setup (which you have) rather than 2 channel setup (or 2.1).  Can't help but wonder if his "formula" is based on having center and side/back surround speakers in the mix and thus maybe overdone?

As for diffusion v absorption behind speakers as w anything it depends--in my room i have a large window behind my speakers and, therefore, opted for absorption (of high/mids) behind the speakers with a curtain rod and heavy drape and it worked well.  When i slide the drape out of the way and play with the the wood venetian blinds of the window (as a diffuser of sorts?) it produces an interesting effect that is not displeasing but seems to de-focus the soundstage.  

Someone above said smaller rooms have different challenges than those addressed in the video and are more challenging. I fall into the wolf garcia crowd of just doing a few things (bass trapping), first reflection and aforementioned absorption and then just enjoy the music (although admittedly i measured frequency response in every part of my room first, mainly for speaker placement and knowing where the bass was emphasized--which, surprise, the usual corners)--i only spent three or four hours total and I'm happy.  As someone else said above, unless your room is really problematic don't obsess over treatment tweaking.

@kota1 That window of mine behind my speakers has been my biggest worry in the room but i went the other route--electing to absorb the sound b/c i was afraid of the highs being emphasized--never occurred to me to go the diffusion route--how much did that "cloud" diffuser cost?  I might have to try that as it looks about as big as my window.  

Found it interesting that Sonitus feels a mixing room is the same as a 2 channel listening room--might have to ponder that -- seems plausible unless the mixing room is also where the player(s) are and then you would think they would generally go for diffusion to mix into the recording rather than absorption to tame reflections.

@tsushima1  Good point.  It's difficult to tell what was "intended" b/c so many recordings are in the studio and then what was 'intended" is up to the engineer--and if the band/artist doesn't like it then you get later remasters if the artist becomes important enough.  But @pedroeb has a point with live music and when i approached room treatment it was from that perspective--tame some room issues b/c our rooms are never as big as even a small venue and there are reflections and mostly bass issues that have to be dealt with.