How to Make a 15'' Speaker Box

Place the 25-by-14 1/2-by-3/4-inch MDF on a work table. These are the sides to the speaker box. Set the blade of the combination square on 3/8-inch. Put the long leg of the head of the combination square on the 3/4-inch edge of the pieces and draw a line on all four sides of the pieces.

Drill pilot holes on the lines with a 1/16-inch drill bit. Drill one pilot hole 1 inch from the corners of the MDF and the others 4 inches apart. Drill 3/8-inch-deep countersink holes in the same place as the pilot holes.

Put some glue on the 14 1/2-inch edges of the 16 1/2-by-14 1/2-by-3/4-inch MDF. These are the top and bottom of the speaker box. Place the glued edges against the matching edge of the sides and secure them with the drywall screws. Clean up the excess glue immediately with a damp cloth.

Lay the 16 1/2-by-23 1/2-by-3/4-inch MDF on the work table. These are the front and back of the speaker box. Center the terminal cup between the 23 1/2-inch edges and 4 inches from one 16 1/2-inch edge on one of the pieces. This becomes the back of the box.

Trace the pattern of the cup onto the MDF. Drill a 3/8-inch hole near one corner inside the pattern. Slip the jigsaw blade into the hole and cut out the pattern.

Position the straight edge on opposite corners diagonally on the remaining 16 1/2-by-23 1/2-by-3/4-inch MDF and draw a line from corner to corner. Repeat this for the other corners. Where these lines intersect is the center point from which to draw the circle for the speaker.

Set the compass at 7 1/8-inches. Stick the point of the compass in the center point created by the lines and draw a circle on the MDF. Drill a 3/8-inch hole inside the circle and cut out the circle.

Apply glue to the edges of the front and back pieces. Slip them inside the frame of the speaker box. Secure them with the drywall screws. Clean up the excess glue with a damp cloth.