Amateur talking pictures and recording (1933)

64 AMATEUR TALKING PICTURES rehearsal is taking place with, of course, the microphone and amplifier switched on. A distinct tremble should be observed. Another method is to tilt back the pick-up and insert an ordinary needle or piece of wire of similar diameter and clamp to it the diaphragm of a cone loud speaker, as in Fig. 31. The quality of reproduction obtained by this means will naturally be poor, but the volume will enable one to correlate that of the actual music and the recorded results obtained later. Of course, a better method is that of monitoring the sound by a loud speaker working at the same time as recording is taking place. This, however, cannot be accomplished Speaker Cone. Wine placed in Needle Ho Id en. Pickup (Tunned Back). Pick-up Arm. Fig. 31. Testing Recording Level unless the recording is in a room separate from the microphone and performers. If a loud speaker and microphone are working together in the same room microphone "howl" occurs. In other words, the microphone passes sound via the amplifier to the loud speaker, which goes to the microphone and back again in a sort of reactive circuit. It is possible that a long room might be employed, but this is not desirable. If loud speaker is to be connected to the output in parallel with the recording head or pick-up a test should be made on the quality of the recording because the addition of the loud speaker alters the conditions of impedance matching. In this connection reference to Chapter IX, page 176, will be useful. Another important point in recording is to make absolutely certain that the room used as a studio is free from articles such as ornaments, etc., which sympathetically