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1925 __ Electrodynamic transducer
Comment : C.W. Rice and E.W. Kellogg perfect the dynamic loudspeaker.The electrodynamic transducer as invented by C.W. Rice and E.W. Kellog in 1925 still forms the basis for the majority of loudspeakers in use today and the principle has only seen marginal changes within nearly 75 years. The widespread use can not be justified by superior performance, in fact the principle of electric-acoustic conversion is limited by numerous fundamental problems, that makes this ultimate stage in the audio chain the weakest – by far. One essential limitation is the striking inefficiency. Generally, a given amount of acoustic power requires orders of magnitude higher power input delivered by the power amplifier. The power amplifier has the task of amplifying the audio signal to a level that, combined with sufficient current to move the coil, produces the desired acoustic level from the loudspeaker. The poor loudspeaker efficiency is very unfortunate, since power amplifiers generally have to be capable of delivering large amounts of undistorted power, to produce the subjective levels demanded by the consumer. (Compiled from various sources)The invention of the loudspeaker : first designed by E. W. Siemens of Germany in 1877 (Edison was busy with the phonograph just at that moment, or he surely would have gotten involved) but perfected by C. W. Rice and E. W. Kellog in 1925, and further by P. J. Walker in 1957 (Dummer 63, 151). The loudspeaker allows electronics to propel a voice, even one in a body which has not developed its voice for projection purposes. This means a performing body no longer needs to train its voice to perform in a large space and be heard by large numbers of people. A person's voice can sound bigger just by applying electronics. (Sam McBride)
Source : McBride, Sam (1997), “Sing the Body Electronic: American Invention in Contemporary Performance”, DeVry Institute of Technology, Sycamore 97.3.
Urls : http://www.oldradio.com/archives/international/japan.html (last visited ) http://audiolabo.free.fr/revue1999/content/anderson11.htm (last visited )

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