resonator
i finished building the helmholtz resonator tonight. here are some photos of the process. first i built the frame out of 2x4s, then i put up some 1x2's on either side of the middle stud and secured straps at 2" deep to hold the insulation in place. then i cut the rigid insulation and put it in place. next came the fabric, which is there for no other purpose than to make the gaps between the slats look nice, and that's partly why the installation is so sloppy (the other reason is i was lacking a decent means of cutting this fabric, which is a pain to cut insofar as fabrics go). finally, i put the slats up after staining them...
the left-hand side of the resonator was an absolute bitch to do, owing to the really tight angle (24 degress on the inside, which meant having to cut everything at its complement of 66 degrees). since things that are capable of cutting/ripping at that angle are few and far between, i had to get creative. mostly it involved rotating the wood 90 degrees before putting it in the pathway of the saw. this sounds easy enough on paper, until you find yourself having to do things like stand a 3-foot piece of wood vertical and pass it along a table saw, or cut pretty much diagonally through a 2x4, which a standard 10" saw can't do. for the frame i had to do the rip cut using the band saw instead. which, as usual, came out very sloppy and i had to go back and plane the hell out of it. i finally got tired of planing and said, "fuck it, it's good enough."
this is what the angle cuts look like on the slats:
i had to pick up a tenoning jig so that i could secure the pieces vertically to run over the table saw. yet another semi-expensive tool that i wsh i didn't have to buy, but it did do an awesome job and if i ever do use it for making tenon joints in woodworking, it has all sorts of knobs and stuff to tweak it out the wazoo.
haven't done another round of room analysis yet, but i do know already that it is not helping with the ringing at 320Hz, or at least not significantly. after walking all around the room and singing that pitch, it sounds like there's only one particular area in the room where the sound energy at that frequency is disproportionately high, so i'm going to tackle the problem by building a smaller, wall-mount helmoltz to go on the wall in the middle of that area.