A loudspeaker, speaker, or speaker system is an electromechanical transducer which converts an electrical signal into sound. The term loudspeaker is currently used for both individual devices and for complete systems consisting of one or more drivers (as the individual transducers are often called) in an enclosure, often with a crossover circuit. It has formerly meant, and perhaps originally, also what is now called a bull horn or in nautical terms, a loudhailer. In Britain, one company, Tannoy, so dominated the field that, in the middle 20th century, loudspeakers were sometimes referred to as 'Tannoys'.
Loudspeakers are used in numerous applications from hearing aids to air raid sirens. Their cost may range from pennies in a cheap radio to high-fidelity speaker systems costing many thousands of pounds. Loudspeakers are the most variable elements in any audio system, regardless of cost, and are responsible for marked audible differences between otherwise identical sound systems.
