When mounting a subwoofer speaker into an enclosure box, it is a common mistake to cut the circular port for the speaker too large. You don't have to start from scratch, but just make a simple modification to make your sub box fully functional. With some commonly found tools and materials you can undo any errors in the construction of your box, saving you a lot of time and money.
Lay your speaker face down (magnet up) on your sheet of plywood or MDF and trace its outline onto the board.
Measure and draw a circle that is 3/4 of an inch inside the circle you traced around the frame of your speaker. Many people make the mistake of tracing the speaker and then cutting along this line, which will be too big for the speaker to be mounted. It is crucial to measure and draw the inside circle in order to have a surface to mount the speaker to.
Draw a third circle 3/4 of an inch outside the traced circle. This is to allow for your speaker mounting plate to be mounted to your subwoofer enclosure.
Cut out the inner circle by drilling a pilot hole and then cutting along the innermost line with your jigsaw.
Cut along the outermost line you drew to produce a ring-like mounting bracket.
Place the mounting ring over the speaker enclosure that you had cut too big. Mount it evenly over the existing hole using plenty of wood glue and some screws.
Attach the hiring harness to your speaker and mount the speaker to your mounting ring and box using the accompanying hardware or some wood screws.
