CABINET REPRODUCERS 



129 



that is diffracted around the baffle and transmitted forward will interfere 

 destructively with the radiation from the front. The response charac- 

 teristics of Fig. 7.8y^ show " dips " in the response when the acoustic path 

 from front to back is a wavelength. Using an irregular baffle, Fig. 7.85, 

 it is possible to reduce this interference and obtain a uniform response 

 characteristic. In this baffle the various paths from front to back differ 

 and the destructive interference is spread over a wide frequency range. 

 The response characteristics of an irregular baffle, Fig. 7.85, show that the 

 dip in the response characteristic of the square baffle is eliminated by the 

 use of an irregular baffle. 



As pointed out in the early part of this chapter, low efficiency at the 

 high frequencies is primarily the result of the inherent mass reactance of 

 the vibrating system. Inefficiency at the low frequencies is primarily due 

 to a small radiation resistance. The large flat baffle is not suitable for 

 commercial sound reproduction in which appearance is a factor. There- 

 fore, most commercial sound reproducers are housed in some form of cabi- 

 net which may be styled to conform with the surroundings. These cabi- 

 nets and other acoustic networks associated with the loud speaker are 

 designed to yield the maximum efficiency at the low frequencies. It is 

 the purpose of the sections which follow to describe some of the means 

 for improving the response of a direct radiator loud speaker at the low 

 frequencies. 



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BACK VIEW 



Fig. 7.9. A direct radiator loud speaker mounted in a typical radio receiver cabinet. The 

 graph shows the pressure response frequency characteristic of this system. 



7.9. Cabinet Reproducers. — The most common housing for a direct 

 radiator loud speaker is the conventional open back cabinet which also 

 houses the radio chassis or phonograph mechanism (Fig. 7.9). These 

 range in size from the largest console type to the smallest midget. From 

 the standpoint of sound reproduction the principle is the same in all. 



