Any suggestions and thoughts what would be a desent basstrap. I am thinking of a rectangular shape that could be hung on the wall or that has wheels. I think it would be made of rockwool. Is thicker always better?
I think the terminology is not set in stone, but I think of "bass" traps as those big (thick, like [MENTION=39487]mjbphotos[/MENTION] says) things that sit floor-to-ceiling in the corners, i.e., where the bass frequencies like to hang out and make trouble. Not generally something movable.
If you want something movable (sometimes called or aka a GOBO) to provide
some isolation between mics, e.g., when you're recording two people playing acoustic guitar in the same room, that's probably going to be thinner than a "bass" trap, and wider, and not ceiling height. The design will be determined kind of by how you plan to use it, and what recording scenarios you want to manage, as well as if you expect to keep them in place for, or in addition to, treatment of the room.
I've got a couple of 3'x4' panels on legs about 1' tall just for the 2-acoustic guitar scenario. The stand on top of short "cubby" things from IKEA (decades ago) so act as wall treatment, though they're about 8" from the wall and not attached. I'm not a mechanical engineer and trying to figure out how to make them wall hangable will have some way to stand them up and not be easily tipped was beyond my ability or interest, TBH. Anyway, they do what I need. I think you'd find a panel of any (usable for mic isolation) size that didn't have some kind of wide bass attached or one it could perhaps snap into would be a hazard, and if the basE/wheel arrangement is wide enough, it's not going to hang nicely. Maybe some wheels brackets that could rotate in place to keep it narrow when hanging and then stable as a free-standing piece, but that gets complicated, heavy, and might add some rattly noises when hanging if you've got loud stuff to record.
P.S.
found some pics I posted here of my space - there's one of the homemade things in this set