TRANSIENT RESPONSE 139 



The mechanical resistance rsM is the sum of all the losses in the suspension, 

 the viscosity of the grill and cloth coverings and the viscosity loss due to 

 the air forced through the slit formed by the air gap and voice coil. 



From equation 7.6 the mechanical impedance Zme due to the electrical 

 circuit is 



(^^)' 7 1A 



Zme = fME = ■ /.14 



rET 



where B = flux density, in gausses, 



/ = length of the voice coil conductor, in centimeters, 

 rET = rsD + Teg-, 



Ted = damped resistance of the voice coil, in abohms, and 

 rsG = internal resistance of the generator (the vacuum tube), in 

 abohms. 

 The mechanical radiation resistance rMR is given by equation 5.10. It 

 may be obtained directly from the graph of Fig. 5.1. 



The mass m is the sum of the cone mass and the mass of the air load 

 upon the cone. The mechanical mass reactance of the air load upon a 

 cone may be obtained from equation 5.10. It may be obtained directly 

 from the graph of Fig. 5.1. 



Heaviside's unextended problem '^-'^ is as follows: Given a linear net- 

 work of n meshes in a state of equilibrium, find its response when a unit 

 force is applied to any mesh. The unit function is defined to be a force 

 which is zero for / < and unity for / > 0. 



The indicial mechanical admittance of the circuit of Fig. 7.3 is 



^« = ^ — 7.15 



rMT + mp -\- — — 



where p is employed as a symbol for the differentiation with respect to the 



independent variable, time. 



Let 



rMT 



a = — — 



2m 



mCn 



^2 Carson, " Electric Circuit Theory and Operational Calculus," McGraw-Hill 

 Book Co., New York. 



1^ Bush, " Operational Circuit Analysis," John Wiley and Sons, New York. 



