Loudspeaker

Loudspeaker A device that converts electrical signals into sound waves. It works in the opposite way to a microphone. The commonest type is the moving-coil speaker, illustrated here. A coil of wire is attached to the apex of a large paper cone and is located between the poles of a permanent magnet. When an electrical current passes through the coil, it sets up a magnetic field.

This field interacts with that of the magnet and causes the coil to be attracted or repelled. This vibrates the cone, which causes sound to be emitted. In HI-FI equipment, saveral separate speakers are included in the speaker unit, each sensitive to a particular frequency range. The high-frequency one is called a tweeter; the low-frequency one, a woofer.