Select your front panel from the pieces of wood. The exact sizes will be dictated by the size of your speaker cones and the size you want your finished speakers to be. Lay the speakers face down on the front panel and draw around them. Remove the speaker cones and cut out the circles using the saw.
Select your rear panel from the pieces of wood. The connection hardware for the speakers will dictate the minimum width of the rear panel, as it will need to accommodate the plate that houses all the audio and power connections. Draw around the connection plate, just as you did with the speakers, and cut the hole.
Measure outward from the side edges of the connection panel to mark what will be the edges of the rear panel. It's advisable to leave a border of at least 2cm around the connection panel to ensure the strength of the box. Use a ruler to extend the two vertical parallel lines to the ends of the piece of wood, then cut to size using the saw.
Measure the width of your front and back panels and set them to one side. Select another two panels from the wood to act as a top and bottom for your box. With the panel in front of you, measure and mark the width of your front panel on the edge nearest to you. On the opposite edge, measure out and mark the width of your rear panel, ensuring it is in the center. Subtract the rear panel width from the front, and halve the remainder. Measure in from the side edges by this amount. For instance, if your front panel was 50cm wide, and the rear was 30cm, make marks on the top edge, 10cm from each side edge. This will leave a 30cm void, exactly in the middle.
Measure from the narrow marks on the top edge to the wider ones on the bottom edge, and cut the sloped sides of the top and bottom panels using the saw. Lay the front panel face down and pipe glue along what will be the top and bottom edges. Position the top and bottom panels and secure them with nails. Allow the glue to set and repeat with the rear panel. This should leave you with a four-sided rectangular frame, consisting of the front and rear panels, connected by the top and bottom pieces.
Lean your side pieces up against the frame and mark them to the correct size. Trim off any excess. Position the sides so that the edges are outside the frame, leaning against it. Otherwise, the angle where the side edge meets the front panel will prevent the two edges from fitting together. Fit one side panel by leaning it flush against the frame and piping glue around the joint from inside the cabinet. Allow it to dry, then secure it with nails.
Install the speakers and connection hardware, screw them into position using their included mounting hardware and connect the wires from the cones to the panel. Test them by connecting them up to a source before fitting the final side panel. Fit the final side panel using screws rather than nails, as this will make removal easier if you need to access the internals again.
Glue the black carpet onto the outer surfaces of the speaker, then fit the corner protectors by screwing them into the panels.