Filed firmly in the “I wish I’d done this ages ago” folder;
in 2010 me and (now wife) made some acoustic panels out of semi-rigid slabs of rockwool (rwa 45 rings a bell, but I honestly can’t remember the exact density) - anyway, they’re approx. 45 x 90 x 10 cm, with a (iirc 5mm thin) solid ply wooden back, and a thicker plank running down the centre for strength.
We made 8 of them, covered them in gauze and then a top layer of tie-died cloth. Then I took them to our lockup room, a typical carpeted walls job, where they actually came in handy over the years. Not so much as excellent room treatment, as there weren’t enough of them for the size of the room, but as baffles for recording; with 6 of them made into a little hutch around a cranked AC30 you could get the spill low enough that you literally couldn’t hear the amp in the drum overheads, even though the kit was right beside the amp.
And the idea of the wooden side was that they could be turned around to make a more reflective surface in the carpeted-wall horror of the practice room; set up in a semi-circle around an acoustic guitar player, they did make a small difference.
The band split up mid-2018, and the acoustic panels were wrapped up in bin liners and left in my garage.
Decided to, for an experiment, see if they made a difference in my little box room studio.
The answer: they make a massive difference. I’m very pleased.