A HIGH EFFICIENCY RECEIVER 153 



r' -\- j ( moo 1, the mechanical impedance of the diaphragm 



aside from that imposed by the horn. 



If r' is negligible, the efficiency of the receiver, i.e., the ratio of power 

 output to power input, is 



Rm 



V = 



Rm + Rd ' 



where Rd is the resistance of the coil when its motion in the field is 

 completely damped. 



