A universal serial bus (USB) subwoofer is a peripheral device that can allow notebook and desktop computers to produce low frequency sounds. Some computer speaker systems make use of the line-out audio jack, though others use a USB port. One type of USB subwoofer is built into a powered amplifier, and has tip-ring-sleeve (TRS) audio outputs for external speakers. Another kind of USB subwoofer is designed specifically for use with notebook computers. Software is typically used to separate high and mid tones from low tones, so that the former can be sent to built-in laptop speakers, while the latter are reproduced by the USB peripheral.
The purpose of a subwoofer is to emit low frequency sounds in the range of about 20-200 hertz (Hz). Sounds that fall within this range are typically referred to as bass, and a sound system that is incapable of producing them may sound hollow or tinny. Simple two channel desktop speakers and notebook computer speakers often lack good bass response, so a USB subwoofer can sometimes be used to improve sound reproduction.
There are two main types of USB subwoofers that can be useful in different situations. One type of USB subwoofer is built into a powered amplifier unit that typically provides connections for two or more other audio channels as well. These systems typically have two or more tip-ring-sleeves or other audio connectors, each of which can be used to hook up a speaker. Other systems have additional connectors that can allow other input devices to be hooked up. These systems use a USB signal to drive both the subwoofer and the regular speakers, so they can be used with both desktop and laptop computers.
The other main type of USB subwoofer is designed specifically for use with laptop computers. Some of these portable computers have excellent built-in speakers, while others lack any bass response at all. Software is typically used to separate out the low tones from an audio source so that they can be sent to the USB subwoofer, while the rest of the sound is reproduced by the built-in speakers. Since only the low tones are routed to the subwoofer peripheral, the overall quality of the sound is still somewhat dependent on the characteristics of the built-in speakers. These subwoofer units are typically smaller and more portable than the full systems that include a powered amplifier and external right and left channel speakers.