A speaker dock is a device that can serve as a base for a music player or other audio device. Speaker docks can serve many purposes, but they are primarily used to charge the docked device and play music from it. As such, they almost always require an external power source; they do not draw from the docked device's battery to play music. In some cases, a company produces both a music player and a corresponding speaker dock for it. In many other cases, however, speaker docks are made by different companies that specialize in audio hardware and speaker systems.
A speaker dock is primarily used to charge and play music contained on a portable audio device, such as an mp3 player. The device typically plugs directly into the dock, allowing for a direct transfer of data and energy. Some docks are made to handle a variety of audio devices, while others are made specifically to handle one style or brand.
The design and quality of speaker docks can vary greatly based on price and purpose. Some are made more as portable charging stations than as high-quality speaker systems; these may have small speakers that do not allow for high volume or high sound quality. Others are made as high-quality speaker systems; these are typically much larger and allow for excellent sound quality. They emphasize some of the subtler aspects of music, such as quiet bass tones. The price of a speaker dock tends to increase based on the quality of its speakers.
Charging and playing music are not, in general, the only functions of a speaker dock. Most also serve as digital clocks and alarm clocks, and many have radio tuners. Most have a "sleep" setting that allows the user to play music for a set period of time before the device automatically deactivates. A speaker dock may also come with a wireless remote, allowing one to change songs and adjust volume from a distance.
Some varieties of speaker docks can actually be used to synchronize music stored on a portable audio device with music stored on a computer, though most speaker docks are independent of the base computer. Some speaker docks are able to connect directly to the computer to allow the files to be synchronized. Others are are able to synchronize files wirelessly over a short distance.