The braces are finished. I had just enough GAF asphalt roofing membrane left from my previous project to use it on these too. Each piece is cut to fit inside each triangular brace area. In the last project I used 3M Super 77 spray adhesive to install the membrane, but it didn't hold well. This time I am using vinyl floor tiling adhesive. It paints on like tan cream, you let it dry clear, then the membrane sticks to it like pressure sensitive adhesive. Much stronger bond than the 77. I only tried a test piece last night, waiting for warm weather to do it outside because it smells.
So I built the crossovers today. Ready to install in the speakers. There is a rheostat L-Pad to adjust tweeter level, plus a fixed 3.3 ohm L-Pad. Other than that it is simple 2nd order Linkwitz Riley, with no impedance correction. This is a simple sloppy assembly to allow listening and tweaking it easier. The crossovers can sit outside the speaker with the driver wires going in through the ports. There is a separate crossover compartment in the bottom of the speaker for the final crossover.
Weather is looking good for the rest of the week.
I am trying to finish them up quick so Shane can at least hear the first rough draft before the 3 month baby sequester begins.
More pictures:
All braces installed. I figured a better geometry for the second box I braced so they are slightly different. The better one is on the left, you can see that there are less interferences of two braces trying to be in the same corner, and easier to remember how to install them with all braces pointing in the same direction. The bottom front brace is vertical instead of diagonal to accommodate the reflex ports which straddle the brace.
A tall pile of 44 triangles of GAF rubberized asphalt roofing membrane for damping cabinet resonance between the braces. The braces raise the resonant frequency to make the damping more efficient. Pieces of wood are the removable floor of the crossover compartment and bottom of the speaker. I accidentally chopped up one of the bottom pieces for braces, so some scraps are collected to make a new one. Fortunately it is on the bottom so appearance doesn't matter.
Crossovers. Nice Erse magnetic core inductors for the bass, Jantzen Superior Z caps, Mills resistors, Dayton LPad. The little aircore coil is for the tweeter, a 20ga cheapie. We have a nice Erse 16ga coil to replace it, but it is lower DCR so we try this first, compare FR to the replacement coil later. Eventually the adjustable LPad (and fixed LPad) will be replaced with a single fixed LPad once we determine the correct value.
The schematic of the crossover designed by Zilch and Pete Schumaker on PE's Tech-Talk forum. Their dialog suggests some other options we can try, like notches and impedance correction, if necessary.