I'm finishing up a half-dozen mega-bass traps this weekend...and I can post some pics when I'm done.
These are meant primarily for the low-end, and not so much for broadband treatment, as I already have enough of that.
It's a bit more of an involved build, though nothing complicated, I just wanted a more custom look, and also specifc purpose....so these are not just bare frames fully wrapped around, etc...but rather finished wood frames w/trim, with the cloth only on the face and the back, since they are not going up against any walls, but are meant to be "mobile" and also free standing.
Basically...6" frames with 6" of OC 703 (three layers of 2" 703) in each trap, with one layer being the 703 FRK (aluminum reinforced paper) type, which acts as a membrane on one side of the trap and helps focus the trapping to the low-end, and the other side will be just a regular 703 layer, same for the middle layer.
That way the traps can be flipped around to either the "hard" or "soft" side.
There's also going to be a layer of polyester felt on both sides, which will simply add to the 703 on the "soft" side, but also prevent too much upper-end reflection on the "hard" side.
Finally some nice Guildford of Main acoustic fabric as the final layer finish layer.
Yeah...a bit overbuilt, plus doing the finished wood frames made it more involved...but I was never crazy about the "stuffed sofa cushion" look that some guys ended up with where they just wrapped sheets of fiberglass or only wanted the front facing traps, with the backs on the walls...so I wanted something different. These are more "gobo" like bass traps...and I actuary plan to also use them in that manner at times, and then for mixing, I can move them in behind my mix position...etc.