File:Racon theater horn loudspeaker.jpg

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DescrizioneRacon theater horn loudspeaker.jpg	English: A large horn loudspeaker made by Racon Electric Co., New York in the 1920s for use in movie theaters and auditorium sound systems, from a 1928 magazine advertisement. Horn loudspeakers were used almost exclusively for large area sound systems into the 1930s since high power cone loudspeakers were not developed and horns could produce 10 times the sound power of a cone for a given amplifier output. Racon specialized in these large theater horns. The speaker consists of a coiled exponentially widening sound tube driven at its narrow end by a compression driver consisting of a small metal diaphragm vibrated by a powerful electromagnet. Since horn loudspeakers had a lower cutoff frequency, large horns with long air columns and wide mouths like this were required to reproduce bass frequencies accurately. It was made of fabric impregnated with a cement hardener, which did not resonate with sound waves as a metal horn would. Alterations to image: cropped out surrounding advertising copy, which said in part: Racon Exponential Air-Column Horns are made in all shapes and sizes up to 6 feet square for Theatres and Auditoriums. Maximum Air Column in minimum space.
Data	marzo 1928
Fonte	Retrieved January 25, 2015 from Popular Radio magazine, Popular Radio, Inc., New York, Vol. 8, No. 5, May 1928, p. 357, on http://www.americanradiohistory.com
Autore	SconosciutoUnknown author
Licenza (Riusare questo file)	This image is from an advertisement for Racon Electric Co. without a copyright notice published in a 1928 magazine. In the United States, advertisements published in collective works (magazines and newspapers) are not covered by the copyright notice for the entire collective work. (See U.S. Copyright Office Circular 3, "Copyright Notice", page 3, "Contributions to Collective Works".) Since the advertisement was published before 1978 without a copyright notice, it falls into the public domain.

Licenza

Quest'opera è nel pubblico dominio perché pubblicata negli Stati Uniti fra il 1929 e il 1977, inclusi, senza un avviso di copyright. A meno che l'autore non sia morto da molti anni, non è nel pubblico dominio nei Paesi o nelle aree che non applicano la regola della durata più breve per le opere statunitensi, come Canada (70 pma), Cina (50 pma, ma non Hong Kong o Macao), Germania (70 pma), Messico (100 pma), Svizzera (70 pma), e altri Paesi con trattati individuali. Vedi questa pagina per ulteriori informazioni.

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