Before gluing the cabinet together, I finished my waveguide mounting setup. The epoxy dried on the waveguide studs, and they seem pretty strong. So next I made some plates from 1/2" plywood scraps to clamp against the back of the baffle. I didn't notice until after I was finished, but the wood grain is going the wrong way on my clamp plates. They seem to work fine, however, so I'm going to stick with them anyway. I did not control the stud positions carefully when I epoxied them, so I held the clamp plates on the ends of the studs and tapped with a hammer to mark the stud positions so that I could drill the holes in the right positions. I also marked the plates and the studs, since the plates are not interchangeable from side to side due to non-uniform stud positions. I drilled the holes one size larger than 1/4" to avoid binding during installation. Fortunately, they slip right on without any fuss. I need to seal the waveguide to the baffle, so I installed 1/4x1/2" high density gray foam weatherstripping around the edge of the waveguide. This foam is highly compressible, and is very easy to bend around the corners on the waveguide as long as you remove the backing paper as you work. I also installed some foam pads of a less compressible foam on the clamp plates, so that there would be foam on both sides of the baffle. I did a test-fit and it works very well.
I stated thinking about how I was going to glue up the cabinet, and I found a way to do it all in one shot. Dadoes would be cool, but I don't have a table saw handy and doing them with a router is too much work. So I had to think up something simpler. I had already glued the double-baffle with smaller inner baffle, so I laid the baffle face-down. The back is the same size as the inner baffle, and so would just fall in if not supported. So to hold it up I just cut four pieces of wood to hold up each corner, to be removed after gluing. Here's a pic of the supports (after gluing):
Before gluing, I did a dry fit and installed clamps to work out a plan:
It is getting pretty cool in the garage, so I put the glue in the house yesterday to warm it up. I also used a radiant heater to try to put a little heat into the wood.
And then I just glued it all up with Titebond 2, installed the clamps, and used a warm, wet towel to wipe off the squeeze-out and drips:
I did end up with one joint that had just enough gap that it didn't seal completely at one end. I think my cut was just slightly out of square, which tends to happen since I seem to forget that plywood sheets don't come perfectly square, even though I know better. I squished in more Tightbond twice to strengthen the joint, and ultimately "caulked" it from the inside with PL Premium when I was gluing the supports inside the cabinet. The rest of the joints were all nice and tight.
Another mistake was that I had the inner/outer out of alignment enough that the outer baffle didn't quite reach the edge in two places, despite the fact that I cut the outer baffle large (to be flush-cut after gluing). I guess I should cut the outer baffle even larger, or be more careful with the alignment next time. I plan to use Bondo to resolve the problem. I also realized that I used a slightly non-parallel strip of wood to align the waveguide recess to the inner baffle, with the result being that the waveguide is just slightly out of square, relative to the box. The misalignment is very slight, and this speaker will be all black and sitting behind a fireplace screen, so I'm not too worried about it. This whole cabinet is less than $30 worth of wood, and I feel like I am learning from the experience, so I'm not too worried about any of these mistakes.
After about 20 hours, I removed the clamps. I did a little inspection and sanding to prepare for the flush-cut bit, and then trimmed up the oversized panels with the router and flush-cut bit. Then I switched to the 1/4" radius round-over bit and did all the edges.
I decided to use "stick" cabinet braces, mostly because I already had some sticks and thought it would be easy. I came up with a plan, cut some additional sticks and two supports, and then did a test-fit:
Once I was satisfied, I used PL Premium to glue the braces to the cabinet and to each other. I used PL Premium because it expands and would help ensure that my supports were making a solid connection to the cabinet.
So now I have a cabinet, almost ready to load:
I plan to run the speaker unfinished for a while, and use a MiniDSP and separate amp channels for the 2 drivers. I guess I could temporarily just drill a hole, run 4 wires through it, and seal it up with a little museum putty or something. But after looking at various binding post options, and realizing that I don't want to install 4 binding posts, I ordered a Speakon connector. It is 4-pole, which should would out nicely during the active phase, and is easy to just use 2 poles once I build a passive crossover.
I was able to pickup a big package of denim/cotton insulation at my local Lowes, too, so I will be using that for stuffing. There's enough of it that I'll probably stuff my Econowaves with it, too, since they currently have just a small amount of polyfill in them. And there's probably enough to stuff many more speakers after that, too.
I expect to have the speaker working this week, and I'm looking forward to hearing how it sounds and playing with some new gear (MiniDSP, new amp, new MiniDSP microphone setup).