RI'.COh'DIXC .INI) Rn.PRODUCING O/- MUSIC AND SI'EFXII 523 



senls tlic old st\le standard machine. Since the vertical scale used 

 in this graph is logarithmic the full difference between the two instru- 



FREOUENCV 



Fig. 20 — Response frequency characteristic of two phonographs. Curve A shows the 



characteristic of the band pass filter type described. Curve B shows the characteristic 



of one of the best commercial machines previously on the market 



Fig. 21 — Bridge for measuring mechanical impedance, being used for determining 

 the impedance of a phonograph horn 



ments does not appear at first glance. Some idea as to the magnitude 

 of this dilTerence can be obtained, however, by noting that the points 

 Pi on the curve of the old machine stands at a power level about 250 

 times as great as P-z- 



