CHAPTER VIII 

 HORN LOUD SPEAKERS 



8.1. Introduction. — Large scale reproduction of sound, involving several 

 acoustical watts, is quite commonplace. Since high power audio fre- 

 quency amplifiers are costly, it is logical to reduce the amplifier output to a 

 minimum by the use of high efficiency loud speakers. At the present time, 

 horn loud speakers seem to be the only satisfactory high efficiency system 

 for large scale sound reproduction. A horn loud speaker ^' 2- 3, 4, 5 consists of 

 an electrically or mechanically driven diaphragm coupled to a horn. The 

 principle virtue of a horn resides in the possibility of presenting practically 

 any value of acoustic resistance to the generator. This feature is extremely 

 valuable for obtaining maximum overall efficiency in the design of the 

 acoustic system. Employing a suitable combination of horns, directional 

 characteristics which are independent of the frequency, as well as practi- 

 cally any type of directional pattern, may be obtained. The combination 

 of high efficiency and the possibility of any directional pattern makes the 

 horn loud speaker particularly suitable for large scale reproduction. For 

 applications requiring high quality reproduction of intense sound, some 

 consideration should be given to the introduction of frequencies not present 

 in the output due to nonlinearity of the operating characteristics of the 

 elements which constitute the vibrating system of the loud speaker. It 

 is the purpose of this chapter to consider the principal factors which influ- 

 ence and govern the efficiency, distortion and power handling charac- 

 teristics of a horn loud speaker and to describe several horn loud speaker 

 systems. 



8.2. Efficiency ^'^'^. — The efficiency of a loud speaker is the ratio of the 

 useful power output to the signal power input. For all large scale repro- 

 duction of sound, efficiency is an important consideration. Specifically, 



1 Hanna and Sleplan, Jour. A.I.E.E., Vol. 43, No. 3, p. 251, 1924. 



2 Wente and Thuras, Bell Syst. Tech. Jour., Vol. 7, No. 1, p. 140, 1928. 



3 Olson, H. F., Jour. Acous. Soc. Amer., Vol. 2, No. 4, p. 242, 1931. 



4 Wente and Thuras, Jour. A.I.E.E., Vol. 53, No. 1, p. 17, 1934. 



5 Olson, H. F., RCA Review, Vol. 2, No. 2, p. 265, 1937. 



6 Wente and Thuras, Jour. A.I.E.E., Vol. 43, No. 3, p. 251, 1924. 

 ' Olson, H. F., RCA Review, Vol. 2, No. 2, p. 265, 1937. 



8 Massa, F., Electronics, Vol. 10, No. 4, p. 30, 1937. 



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