When I first read this thread a while back I didn't think much applied to me and my "Brand New" (to us) home we had just moved to.
Then a few days ago, my wife was prompting our daughter to hasten progress on her room and the subject of this modern foldable foam mattress, temporarily dropped in a corner during the early stages of the move came up. The foam thing is made to fold into a cube or turn into a Twin XL sized mattress. She has a nice bed now and has no use for this temporay thing she bought while we were re-doing her bedroom in the old house last year.
I remembered having read this thread!
Wait! I have an idea. Let me take it for a while.
I unfolded it into a mattress and stood it sideways against the wall behind my speakers. As a way to help it just stand on its own, I angled the middle folding part toward my equipment rack. It's been there ever since, but I don't even have my whole set up "set up," yet. Any critical listening will have to wait a while, but it definitely changed a lot of things in my new "hard" surface listening room.
I immediately found it to be a half decent bass trap. But, now, coming back to this thread, I want to play with that angle in the middle, making it even steeper and maybe moving it even closer to the rack. And listen more closely, of course.
Happy accident? Maybe so. Might be onto something, but my first instinct is that ANYTHING I put there would have helped some.
Can't do a Blind Test, but it will be easy to move in and out for comparison purposes. Maybe it just needs to be re-folded into a cube and used to "sound shadow" the back of my rack.
Thanks for the idea, guys. It is a very cheap thing to play with and if it helps, WOW, cool!