Building a 4x12 guitar speaker cabinet can save you money and allow you to customize your sound by using different woods to build the cabinet, speakers and electronics in the cabinet. By building your own cabinet, you can experiment with speakers of different brands and wattage. Use Baltic birch, pine plywood or medium-density fiberboard (MDF) for the cabinet. See which tones you like best. Build an extension cabinet for an amp, or use as a half-stack with a guitar amp head for shows, in the studio or just to jam with your friends on the weekends.
Cut two pieces of plywood or MDF to 28 inches by 28 inches for the front and back of the 4x12 cabinet.
Cut two pieces to 14 by 30 inches for the top, bottom and two pieces 14 by 28 for the two sides of the cabinet.
Draw circles for the speakers on the front panel of the cabinet with a compass or large protractor. Find the center of each speaker and draw a four 12-inch circles, one for each speaker cone. Drill a starting hole in the center of each circle, then carefully cut out each speaker hole using a router or jigsaw to follow the inside of the circle line to make sure the holes are not too large. You can sand or file the wholes larger if needed.
Cut the back panel of the cabinet for the speaker jack. Draw the shape of the jack onto the back panel and cut it so it sits flush with the back.
Construct the cabinet frame. Glue the top, bottom and sides together and allow them to dry thoroughly. Screw the cabinet together where the edges meet to strengthen the frame.
Screw and glue the back panel to the frame. Seal the real panel using epoxy to ensure that no air escapes out of the rear panel.
Attach the speakers to the front panel with screws. Attach the speaker wire to the speakers and feed them through the hole in the rear for the jack. Screw the front panel to the rest of the cabinet.
Connect the speaker wires to the jack and screw the jack into place on the back panel. Make sure the jack is wired according to the instructions it came with.