File:Theater horn loudspeaker 1928.jpg
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[edit]DescriptionTheater horn loudspeaker 1928.jpg |
English: Large horn loudspeaker from 1928 built for use in movie theaters and concert halls. Because early vacuum tube audio amplifiers couldn't produce much power, and horn loudspeakers can produce about 10 dB more sound power from an amplifier than a cone speaker, loudspeakers in theaters until WW2 were horn speakers. In order to reproduce bass frequencies adequately the horn had to be large, with a wide mouth and a sound path of 12 - 18 feet. This was a standard theater horn made by Bell Telephone Laboratories in New York for sound research. Scientist S. P. Grace holds a replica of Alexander Graham Bell's original telephone "loudspeaker" transmitter for comparison. |
Date | |
Source | Retrieved July 19, 2014 from G. C. B. Rowe, "The 'Electric Brain' and its language" in Radio News magazine, Experimenter Publishing Co., New York, Vol. 9, No. 12, June 1928, p. 1322 archived on American Radio History website |
Author | G. C. B. Rowe |
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This 1928 issue of Radio News magazine would have the copyright renewed in 1956. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. [1] Search of the Renewals for Periodicals for 1955, 1956 and 1957 show no renewal entries for Radio News. Therefore the copyright was not renewed and it is in the public domain. |
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This work is in the public domain because it was published in the United States between 1929 and 1963, and although there may or may not have been a copyright notice, the copyright was not renewed. For further explanation, see Commons:Hirtle chart and the copyright renewal logs.
Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties. العربية ∙ Deutsch ∙ English ∙ español ∙ français ∙ galego ∙ italiano ∙ 日本語 ∙ 한국어 ∙ македонски ∙ português ∙ português do Brasil ∙ русский ∙ sicilianu ∙ slovenščina ∙ українська ∙ 简体中文 ∙ 繁體中文 ∙ +/− |
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current | 13:00, 23 July 2014 | ![]() | 772 × 616 (136 KB) | Chetvorno (talk | contribs) | User created page with UploadWizard |
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