Bookshelf Speakers

A loudspeaker, or simply speaker, is an electromechanical transducer which converts an electrical signal into sound. more...

The term loudspeaker is used to refer to both the device itself, and a complete system consisting of one or more loudspeaker drivers (as the individual units are often called) in an enclosure. The loudspeaker is the most variable element in an audio system, and is responsible for marked audible differences between systems.

History

Nikola Tesla is believed to have put electrically charged carbon dust in a cup-shaped device to create the first telephone loudspeaker. However, the first documented device that might fit this description was created in 1881.

Alexander Graham Bell patented the first loudspeaker as part of his telephone in 1876. This was soon followed by an improved version from Ernst Siemens in Germany and England (1878). The modern design of moving-coil loudspeaker was established by Oliver Lodge in England (1898).

The moving coil principle was patented in 1924 by two Americans, Chester W. Rice and Edward W. Kellogg. There is some controversy in that an application was made earlier by the Briton Paul Voigt but not granted until later. Voigt produced the first effective full range unit in 1928, and he also developed what may have been the first system designed for the home, although using electromagnets rather than permanent magnets.

These first loudspeakers used electromagnets because large, powerful permanent magnets were not freely available at reasonable cost. The coil of the electromagnet is called a field coil and is energized by direct current through a second pair of terminals. This winding usually served a dual role, acting also as a choke coil filtering the power supply of the amplifier which the loudspeaker was connected to.

The quality of loudspeaker systems until the 1950s was, to modern ears, very poor. Developments in cabinet technology (e.g. acoustic suspension) and changes in materials used in the actual loudspeaker, led to audible improvements. For example, paper cones (or doped paper cones, where the paper is treated with a substance to improve its performance) are still in use today, and can provide good performance. Polypropylene and aluminium are also used as diaphragm materials.

Read more at Wikipedia.org