A transducer that converts electrical energy into sound energy, providing the audible sound in equipment such as public address systems, studio monitors, guitar or bass amplifiers, radios, televisions, and home stereos.
A standard dynamic loudspeaker consists of a voice coil, a magnet, a diaphragm and a cone. The electrical energy output of a power amplifier is transmitted as voltage over a wire to the voice coil. The current flowing through the voice coil produces an electromagnetic field that reacts with the stationary magnet in the speaker assembly. The voice coil is attached to a diaphragm, which in turn is attached to the cone. The magnetic fluctuations cause the diaphragm and thus the cone to move, moving air and radiating sound.
There are other types of loudspeaker technology, the best known being electrostatic speakers. These differ from dynamic loudspeakers in that they consist of a thin sheet of electrically conductive film suspended between two wire screens. A high-voltage charge is applied to the film and it is alternately attracted to one screen and then the other. This creates motion, which again radiates sound. Another type of loudspeaker are servo drive loudspeakers. These employ servo driven motors attached to the speaker cone in place of the magnet/wire assembly. This type of speaker is generally only used in subwoofer applications, and even then only rarely.