156 



HORN LOUD SPEAKERS 



where Tmh = radiation resistance at the throat of the horn, and 



Tma = radiationresistanceof the back of the diaphragm from Sec. 5.7. 

 Both in the same units. 

 The characteristics depicting the loss due to radiation from the back of 

 the diaphragm for diameters of 2, 4, 8, and 16 inches and various ratios of 



THROAT 

 DIAPHRAGM DIA?21N. AREA=3.I4 SQ.IN. AREA 



ISO IN 



THROAT 

 DIAPHRAGM D1A^4IN. AREA= I2.56SQ.IN. AREA 



SQ.IN. 



1000 

 FREQUENCY 



THROAT 

 DIAPHRAGM DIAralN. AREA = 50.2SQ.IN. AREA 



■ SQ IN 



50.2 

 100. 



1000 

 FREQUENCY 



THROAT 

 DIAPHRAGM DIAFI6 IN. AREA=20I SQ.IN. AREA 



ISQ IN 



25.1 

 50.2 

 100. 



201. 

 402. 



Fig. 8.7. Characteristics depicting the loss in per cent of the total radiation, due to the 

 radiation of sound from the back of the diaphragm of a horn loud speaker for diameters of 

 2, 4, 8 and 16 inches and throat areas of 2, 1, J, | and | times the diaphragm area. 



throat area to diaphragm area are shown in Fig. 8.7. These characteristics 

 show that the loss is indeed quite high. 



8.3. Nonlinear Distortion. — In general, the power input to (or the 

 power output of) a loud speaker is limited by the generation of spurious 

 harmonics or subharmonics. The limiting factor may be due to air 

 overload, excessive amplitudes where Hooke's law no longer holds, non- 

 linear elements, variable voice coil air gap flux product or nonfundamental 

 vibration modes of the diaphragm. It is the purpose of this section to 

 consider the most common forms of nonlinear distortion in horn loud 

 speakers. 



A. Distortion Due to Air Overload in the Horn i^, i7, i8_ — ^ sound wave of 

 large amplitude cannot be propagated in air without a change in the 

 wave form and, as a result, the production of harmonics. If equal positive 



i^Rocard, Comtes Rendus, Vol. 196, p. 161, 1933. 



^^ Thuras, Jenkins and O'Neil, Jour. Acous. Soc. Amer., Vol. 6, No. 3, p. 173, 1935. 



18 Goldstein and McLachlin, Jour. Acous. Soc. Amer., Vol. 6, No. 4, p. 275, 1935. 



