RECENT ADVANCES IN WAX RECORDING 



171 



same time the transmitting structure has been so designed that a 

 very broad range of frequencies is properly transmitted from the 

 needle point to the armature. Moreover, proper mechanical loads 

 have been provided so that the motions after transmission are absorbed 

 and hence not reflected back. This is another way of stating the fact 



500 1000 



FREQUENCY 



Fig. 11 — Response of a 4-a pickup driven by constant velocity pressings. 



that resonance as ordinarily considered has been eliminated from 

 these structures. 



The curves shown in Figs. 10 to 12 illustrate the steps which have 

 been taken. The pickup shown in Fig. 11 is free from the resonances 

 shown in that of Fig. 10. The resonances present in the earlier 



Fig. 12— Response of experimental pickup driven by constant velocity pressings. 



pickup involved high needle point impedances in the region of these 

 resonances. These high impedances involved large driving forces 

 destructive both to needle and record. Certain records were injured 

 after only a few playings with this reproducer. The later reproducer 

 is characterized not only by considerably reduced average needle 

 point impedance, but, as shown by the curves, the resonance is 



