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Thursday, August 18, 2011

History Of Speakers


A speaker is a device that converts electrical signals to sound waves. It is a transducer; a transducer is a device that converts one form of energy to another. Speaker may be referred to just one transducer or an integration of many transducers and filters. For a speaker to give the highest possible degree of quality sound, we must incorporate more than one transducer to output a wide range of frequencies.

The first electrical speaker device was constructed and patented by Alexander Graham Bell in 1876 for the purpose of making the telephone. Later Ernst Siemens and Nicola Tesla improved over Bell’s invention in 1877 and 1881 respectively. Horace Short patented a loudspeaker design that uses compressed-air mechanism in 1898. Pathe and Victor Talking Machine Company were few companies that incorporated the compressed-air speakers in their players but the sound quality was poor and producing low volume sound was not possible.

In the more advanced design we use moving coil transducer, which was patented by Chester W. Rice and Edward W. Kellogg in 1924. The moving coil transducer used electromagnets as permanent magnets were costly at that time. It was only in the 1930s that filters were used in the speakers to increase the level of sound pressure, frequency response and overall quality of the device output. The Shearer Horn System for Theatres was the first speaker system of industry standard that was installed in 1937. This speaker system was installed by Metro-Goldwyn-Mayer, an American media company that is in production and distribution of TV programs and movie. This system was designed by John Kenneth Hilliard, Douglas Shearer and James Bullough Lansing. It consisted of four 15" low frequency drivers, a 375 Hz crossover network and a single sectoral horn with two air-compression transducers that respond to high frequencies. Many improvements have been made on the speaker like development in cone materials, inclusion of high-temperature bonding agent, improvement on permanent magnet materials, improved techniques for measurement, finite element analysis and designing of speakers using the aid of computers.


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