A subwoofer is a speaker that is designed to reproduce very low bass frequencies (usually those between 20 Hz and 125 Hz). These speakers tend to be large in size (between 8" (20.3cm) and 15" (38.1cm) in diameter) and require more power to operate than their small speaker counterparts. A subwoofer is used in order to provide the powerful audio rumble or punch commonly used in movies and music.

Common uses of subwoofers include installation in one's car or, more commonly, in home theater use. In either application the subwoofer is not considered a stand alone device but helps to fortify the higher pitched sound produced from the speakers. While never entirely necessary to reproduce sound from a car or home audio system, subwoofers have reached great popularity due to their ability to pack a large, low frequency punch in a small space.

The quality of a subwoofer depends mainly upon its construction and the components used in manufacturing it. Subwoofers can be made out of many different materials including reinforced paper, polypropylene, Kevlar®, carbon or aluminum. Each material provides a slightly different effect or sound.

Further enhancing the sound of subwoofers are their enclosures. Enclosures are used for subwoofers in order to mount them and give them room to create their booming sound. Many different types and sizes of subwoofer boxes exist and each achieves a different sound effect and volume level. Several home theater systems include a subwoofer that matches the speakers and amplifiers provided. In this case, your work is done for you. However, if purchasing a subwoofer to add to your home system or car audio setup there is an important distinction to consider: Mounted or unmounted?

Subwoofers can be purchased in their basic form, which is unmounted and not yet ready to be used, or can be purchased already installed in a box. Pre-enclosed subwoofers save the user the hassle of matching the box to the subwoofer and getting it installed properly. On the other hand, unmounted subwoofers allow the experienced consumer to customize their setup by picking a box to fit their installation needs and sound preferences.