Adjust the miter saw to cut a 45-degree angle by loosening the handle and turning the miter saw table until the gauge aligns with the 45-degree mark. Tighten the handle to lock the saw in place.
Cut each end of the four hardwood boards at a 45-degree angle using the miter saw. Guide the saw down through the wood and raise it back up to the start position to complete each cut. Make the cuts so they angle toward each other.
Fit the boards together to form a square assembly. The mitered, 45-degree ends should fit together like the corners on a picture frame. Hammer four evenly spaced finish nails through each joint to fasten the assembly together.
Center the plywood panel over one end of the assembly. This is the back panel. Hammer finish nails through the panel into the edges of the assembly every 2 to 4 inches to secure it in place.
Drill a 1-inch hole in the center of the back panel using a drill equipped with a 1-inch hole saw.
Center a nail set on each finish nail head and tap the top of it with a hammer to set each nail 1/16-inch below the surface of the wood. Fill each hole with wood putty using a putty knife. Leave the putty slightly raised to allow for some shrinkage while it dries. Allow the putty to dry for 24 hours.
Sand the putty flush with the surface of the wood using a fine-grit sanding block. Brush an even coat of wood finish over the wooden assembly. Allow the finish to dry at least four hours and apply a second coat. Wait 24 hours for the finish to dry before continuing with the project.
Turn the assembly over so that the open side is facing up. Place the speaker inside the assembly with the front side facing up. Feed the wires back through the 1-inch hole in the back panel. Center the decorative metal panel over the open side of the assembly. Drive a decorative head screw through each corner of the metal panel into the edges of the assembly with a screw gun. The mesh panel can be removed easily by removing the four screws when you need to take the speaker out of the box.