Last night I glued up the main cabinet! The backbox was done a few days ago. It took a couple of extra hands, but it’s all together now.
I abandoned the lock miter joint due to its complexity. I’m not a professional cabinet maker, and the chance that I mess up one cut out of sixteen was pretty good and would increase my materials cost by 50% (about $90 for this nice 3/4″ Baltic birch plywood). So I went with a spline joint that could easily be cut on the table saw.
The nine 1″ holes in the bottom of the cabinet are where the down-firing subwoofer will be located. The small cutout near them is for a C14 power socket.
My next few steps include adding the leg braces and drilling holes for leg bolts, priming and painting, and attaching the backbox to the main cabinet.