Both speaker boxes are built!
Now it's time for internal bracing. Bracing does not stop vibrations. All a brace can do is shorten an unsupported span. In doing so, the brace works like a finger on a guitar string. The string still vibrates, but at a higher frequency. The panel vibrating at higher frequency has much less energy than if it were vibrating at low frequency, so it is easier to damp. More on damping later. But for now I am trying to decide the geometry of the bracing.
The tri corners are the most rigid mechanical ground of the speaker, with side corners next best. I would like to refer the bracing to glued corners in some way to get extreme rigidity from the brace. The designer's plan calls for bracing which connects the center of one membrane to the center of the opposite panel. So in theory, both can vibrate together in sympathy, which they would do because they are made from same material and have the same span. Connecting the braces to the immovable corners will stop the membranes from moving.
The problem is that the bracing must be built into the speaker before the side panel is glued on. I am skinny, but not skinny enough to climb up inside the horn, so the bracing and damping has to be finished before the side lid can be glued on. The good part is that when a brace is viewed as a strut to raise freq then all considerations of strength and beefiness are out the window and only a small contact area and thin rod is necessary. Picture carbon suspension struts on a race car.
I think I will use 3/4" square rods cut from plywood, but the alternatives are wood dowel, or steel strapping. Steel would require bending a bead to stiffen it. Whatever material I use for strut I will dampen the strut vibes later.
