I want them to be so thick that they would stand on the floor by themselves so yeah, 6-8" easy, more like 30 cm which is around 11" I think
I'd be looking at Safe n Sound or even attic insulation (pink fluffy, as it's generically called) if you're talking about that sort of depth.
Go here to play around with absorber depths and gas flow resistivity (GFR) values to determine the best GFR for the depth you want. The thicker the trap, the lower you want the GFR to be. GFR kind of sort of correlates with density, but not exactly, so the lower the density, the lower the GFR tends to be, but you still really want to choose products based on demonstrable GFR values.
Then go here to see what product has the appropriate GFR, that is available for purchase where you live. On the last few pages of this thread, is also a few posts where the relevant spreadsheet is updated and linked, where the everything is listed.
Curious -- are you going to cover all your walls with the panels?
I want one on the front wall (yuuuge window), in the front corners and on the left/right. There is a huge wardrobe on the back wall, it will be filled with soft stuff and the doors will be left open, so it will act like a big-ass bass trap
You have a good plan, linas, and YES cover them! Two layers of a durable cotton blend upholstery fabric from any local fabric/sewing outlet store. There's always one with 5 miles of a retirement home as old ladies love to sew! (and so do I even though I am neither old nor a lady HAHA)
Would enough of these be good? I want to stick them to the wall, I don't want to make holes in the wall
not sure about batting made of recycle PET bottles? But also not sure if health risks are greater than any other product. I've used OC703, Rockwool, and Insulcot (a recycled cotton batting - really nice since it's NOT itchy fiberglass, and close to absorption of the others, but might be discontinued?) . Still I'd personally be a little cautious with that one.
If you don’t want to build them yourself I have found GIK is the best bang for buck. They sell soffit traps, monster bass traps (7”), 5ft standing bass traps (4”). GIK panels are not too expensive and very effective.
If you decide to build them yourself you might end up spending more money. I’d be willing to share How I built mine with anyone interested (see pics). But, they cost more than GIK panels because I wanted a wood frame. They could be built cheaper (see corner trap)