To build a 12-inch subwoofer box you need three-quarter-inch medium-density fiberboard, 2-inch drywall screws and either half-inch or three-quarter-inch panhead sheet metal screws. Other materials and tools that are required include carpenter's glue, a jigsaw saw, an electric drill, silicon caulk, non-hardening rope caulk and a speaker terminal cup. Most importantly, a subwoofer of the appropriate size is also required.
To design and build a successful subwoofer box, take into consideration the dimension and shape of the box. First, think about how much space is actually available in the vehicle for a subwoofer box. The shape of the box, as well as the basic dimensions of height, width and depth, must conform to the space available in the car. Certain cars may lack space for a rectangular subwoofer box, so a wedge shape may be necessary. Once you've taken the measurements, make a quick sketch of how you want the finished box to look, then build the box using the supplies and tools you gathered.
Once you complete the construction of the subwoofer box, connect the subwoofer inside to the car's amplifier and speaker system to create a complete system. Once the subwoofer box is functional, you can customize its outside appearance based on your personal preferences or those of the car owner.