I purchased 100 board-feet of solid cherry from internetlumber.com and used less than half to construct ten speakers. I had to join several 5" wide boards to create 10" wide sections for the front and back panels. Total cost for wood with delivery was approximately $450. MDF would be a less expensive option.

Each speaker enclosure was constructed from the following parts:
(2) Side panels: 11-1/2" x 6" x 3/4"
(1) Top panel: 9" x 6" x 3/4"
(1) Bottom panel: 9" x 6" x 3/4"
(1) Front panel: 11-1/2" x 9" x 3/4"
(1) Back panel: 11-1/2" x 9" x 3/4"
(8) Horizontal internal braces: 6" x 3/4" x 3/4"
(4) Vertical internal braces: 8" x 3/4" x 3/4"
The side panels were mitered to 45° on both 6" sides (maintaining the exterior dimension of 11-1/2"). The top and bottom panels were mitered to 45° on both 6" sides (maintaining the exterior dimension of 9"). This permitted the side panels to meet with the top and bottom panels, making a 90° corner. All four edges of the exterior facing sides of the front and back panels were routed with a half-over router bit. All parts were biscuit joined, glued, and screwed together to ensure a solid enclosure. Holes were pre-drilled for all wood screws. All internal seams were fi lled with clear silicon caulk to keep the box airtight, and the enclosures were lightly fi lled with Acousta-Stuf.