Since 1950, SEAS has been building high-end loudspeaker drivers that compete with Altec and JBL loudspeakers. Even today, the moving-coil loudspeaker driver remains the most popular type of electroacoustic speaker component. SEAS components come at a fairly hefty price, but their performance produces recording studio quality in any environment. For a DIY two-way speaker that delivers outstanding sound reproduction in a computer or surround sound system, a SEAS 4.5-inch driver paired with an SEAS 1-inch tweeter will work well.
Build speaker cabinets with 3/4-inch birch plywood, or purchase ready-made cabinets.
Cut the birch plywood box pieces to size. (Skip this step if buying a finished speaker box or box kit.) Using a circular saw or table saw, cut the top, bottom, and sides. Top and bottom pieces are 4-1/2 inches by 4 inches. Sides panels are 4 inches by 8-1/2 inches. Front and back panels are 6 inches by 8 inches.
Cut a 6-inch segment of 3/4-inch ID (inside diameter) PVC pipe down to 5 inches with a hacksaw. This becomes the port that augments the low-end response of the SEAS woofer.
Glue the side panels, bottom panel and top together. Top and bottom pieces are inset. Use generous amounts of high-quality wood glue to join the panels. Further secure the panels by screwing 1-inch wood screws in each corner of the box sides. Add two more wood screws at the midpoints of the sides. Clamp the box with C-clamps while drying. The C-clamps can be removed after one hour, but allow eight hours for the assembly to fully dry.
Make the back panel cutout for the terminal cup. Use a drill and sabre saw to make the cuts. Apply wood glue to the surface edges of one side of the box, and press the back panel in place. Drill 1-inch wood screws in all four corners, plus two additional screws countersunk at the midpoint of the long sides of the back panel. Clamp for an hour. Install the terminal cup or box in the back panel with glue, and glue the crossover to a side panel within the box.
Draw circles on the front panel for the SEAS woofer, tweeter and port. Trace a 4-1/2-inch circle shape near the bottom, and trace 1-1/4-inch and 3/4-inch diameter circles above the larger circle. Use a hole saw or router to make the cutouts. Maintain a space of 3/4 inches between the woofer and the other cutouts. Flange the smaller port hole 1/8 inch larger at the panel surface. Channel cut the speaker holes 1/8 inch so the speakers mount flush with the wood surface.
Apply a bead of silicone caulk along all interior box joints. Let the caulk dry for 10 to 12 hours. While the caulk dries, glue acoustic foam or other sound-absorption material to all interior surfaces of the box, around the crossover and terminal cup.
Glue the PVC pipe to the back of the front panel. Attach the tweeter and woofer to the opposite side of the front panel, applying a thin bead of non-drying caulk before screwing both speakers in with wood screws. Attach 12-gauge speaker wire between the terminal cup and the crossover. Also attach 12-gauge speaker wire from the crossover to both the tweeter and the woofer connection terminals.
Attach the front panel to the box with wood glue. Screw to further tighten as with the other panels, and clamp the front panel to ensure an airtight seal.
Fill the countersunk screws' holes with wood putty. Sand the entire cabinet surface with a sanding block or electric sander. Paint, stain or apply a wood veneer to finish your SEAS DIY speakers.