Here's a good one. This is a 1.5 cubic foot sealed box for a single SW-12-04 Direct Servo sub.
This is the inner box. It is built from 3/8" thick MDF on four sides.
The braces are 2.875" apart and are made from 3/4" MDF. The woofer mounts in the front (as shown) and the plate amp will mount on the panel on the rear.
Next some 3/4" wide and 3/8" thick MDF strips are cut and laid in line with the braces below.
When this is set into the outer box it leaves a 3/8" thick space between the walls.
Next five sides of the outer box is built around it.
Additional 3/4" thick pieces cover the front (where the woofer mounts) and the back panel where the amp will mount.
Then comes the fun part, pouring in the sand. Shaking it, rocking it, and beating the sides with a rubber mallet insured that the sand was forced in as tight as possible and as much as it could hold.
Then the last panel is glued on sealing it up.
So far, so good. It is a rock solid box.
Next I cut the amp hole in the back.
I also plan to seal the back of the amp from the inner air space.
More to come...