A speaker is an electronic device used to transform varying electric current into audible sound. It usually consists of a speaker cone, most often made of plastic or cardboard, which is moved by magnetic forces induced by the electromagnet to which the input signal is directed.
An active speaker contains a built-in amplifier to process low voltage sound signals, while a passive speaker requires an external amplifier.
The most important properties of a speaker are its impedance (expressed in ohms), power handling capability (in watts), and its frequency output range, which determines the range of sounds the speaker is able to produce.
