140 



DIRECT RADIATOR LOUD SPEAKERS 



The indicial admittance may be written 



1 poi 



A{t) = 



mui {p + a.y + co^ 



From tables of operational formulas, the solution is 



moo 



sm co/ 



7.16 



7.17 



Figure 7.16 shows the effectof the impedance of the vacuum tube upon the 

 transient response of a loud speaker. In this case the loud speaker is con- 

 nected to the following generators: a very high impedance corresponding 

 to pentode or Class " B " operation; a generator of one half the resistance 



a <o 



r^-^ZZ 



0.05 

 TIME IN SECONDS 



Fig. 7.16. The transient response of a 12-inch loud speaker to a unit force for various types 

 of generators. J. Generator of very high resistance. B. Generator having a resistance of 

 one-half of the loud speaker impedance. C. Generator of zero impedance. 



of the loud speaker corresponding to class " A " operation; and to a gen- 

 erator of very low impedance corresponding to inverse feedback operation. 

 The impedance characteristic of the loud speaker is shown by the upper- 

 most left-hand graph of Fig. 7.17. This example shows that the damping 



