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BELL SYSTEM TECHNICAL JOURNAL 



under the control of the mixer operator in the monitoring room, 

 viewing the set through a double window in the studio wall. The 

 mixer controls also the gain of the amplifiers for the recording machines. 

 The diagram shows relays which permit the mixer to connect the 

 horn circuit either directly to the recording amplifier or to one or the 

 other of the monitoring photoelectric cells in the film recorders. 

 The direct connection is used in preparing the sound pick-up in the 

 studio: the program is rehearsed until satisfactory arrangement of 

 microphones and of amplifier gain is effected. The electrical charac- 



AMPLIFIER ROOM 



MUALizER-B-PRE- | RECORDING ROOM 

 FERABLY A CONSTANT! 

 IMPEDANCE EQUALIZER 



D-86692 

 AMPLIFIERS 



-T?-^ /fy-540-AW 



N^ U/ CONE I 



MONITOR ROOM I ^^ I 



Fig. 4 — Schematic diagram of the studio equipment for sound recording. 



teristic of this direct monitoring circuit is so designed that the sound 

 quality heard in the horns shall be the same as the quality to be 

 expected in the reproduction of the positive print in the theater. 

 Acoustic treatment of the walls of the monitoring room secures the 

 reverberation characteristic of the theater, and the monitoring level 

 is so adjusted that the mixer operator hears the same loudness that 

 he would wish to hear from the theater horns. It is capitally im- 

 portant that the operator judge his pick-up on the basis of sound 

 closely identical in loudness and quality with that to be heard later in 

 theater reproduction. 



After the pick-up has been established on the direct monitoring 



