I’ll be honest from the beginning; designing and building a subwoofer needs a little more effort than simply buying a woofer and mounting it in a wooden box. But unlike designing a full range loudspeaker, which needs careful adjusting of the individual loudspeakers, it is easier to design and construct a good subwoofer. This is because a subwoofer works in the lower regions of the sound spectrum where the human ear is least sensitive. In essence a subwoofer design is a piston design, much like the pistons in your car engine, moving back and forth in a very limited frequency range. Obviously the basic principle of a subwoofer is to extend the bass response of your loudspeakers, or add some extra push to the lower regions of the sound spectrum for home theatre use. Due to the limited frequency range a subwoofer operates in, usually between 20 to 100Hz, all that is usually required is a large woofer able to move a lot of air in a properly calculated enclosure.