GIK acoustic panels

The most effect for the least material is a triangle shape in the upper ceiling corners. 12" on a side is plenty.

Next most effective is vertically where the walls meet, and horizontally where the walls meet the ceiling. 12" wide by however long you want to treat.

The most common material used is Owens Corning 703  https://www.google.com/search?q=owens+corning+703&rlz=1C1GGRV_enUS765US765&oq=owens+corning+... It comes in different thicknesses, is available all over, and if you hunt around they even have a spec sheet with graphs showing acoustic absorption of the different panels by frequency. OC703 cuts easily with scissors or knife, or like butter with a table saw. Its light enough to be put up with little push pins that leave an almost invisible hole in the wall, making it trivial to experiment with locations.

Then when you settle on what and where its easily covered with whatever fabric you want. Just be aware your choice of fabric will affect performance- the more transparent like speaker grills the less change, the more tight and strong the weave the more it will reflect like any other surface.

Thanks @millercarbon.I did consider making my own but GIK is able to make their traps with 'range limiters' so they will absorb a bit more bass and leave the high frequencies alone which intrigued me.It's a lot more expensive unfortunately than diy,sigh....but worth it so far to get the professional help and support from GIK and to fine tune the room.They have such a variety of diffusers,scatter plates,etc. that's beyond my expertise.Plus they are returnable so I took the plunge🙂

@erik_squires  my speakers are (shhhh) Tekton Impact Monitors.Today I moved everything out of the living room and played around with positioning the panels and speakers.Right now it's sounding pretty darn good.The four corners have the 244s with range limiters plus the 2x2 spot panels(range limited) resting on top so it's almost floor to ceiling.Tomorrow I will hang the 244s by themselves so they are touching the ceiling and experiment with placement of the spot panels.The monster trap is behind the console on the front wall along with all three of the 242s.One is on top of the monster (think letter T).The 242s had no effect on each side to capture reflections there.I propped one behind my listening chair and didn't care for that much absorption.Diffusion would be better or perhaps even a wall hanging,or leave well enough alone🙂

So anywho,I'm really happy with the smoothed out bass.The windows are not the problem I thought they were at all!In my squarish room the front wall and corners seem to be most important.Next up is treating the wall/ceiling junction.I'll move the spot panels around singlely and in groups and see what happens.

Check out www.readyacoustics.com I ordered several years ago. Don’t know how they price/configure now. They have their own fabric ready made to cover the OC. I actually have several I’m not using if interested?

Thanks slaw!I'll check with you first if I end up needing more.Still moving the panels around and experimenting....