American cinematographer (Oct 1929)

Fourteen American Cinematographer October, 1929 Recording (Continued from Page 9) state. From the standpoint of the changes involved, synchronizing and re-recording arc similar, as shown on Figures 5 and 6. Fig. 8 These latter processes involve 25 changes of condition when rc-rccording from film to film and 22 changes of condition from disc to disc. The changes in condition in the re-recording process are as follows: It was found desirable to arrange the amplifiers in the repro- ducing circuit so as to reduce mechanical vibration to a minimum. Special amplifiers were built to meet the requirements of re- recording work. It was also necessary to carefully guard against noise being introduced by circulating currents and foreign potentials. The process of recording is such that there is a tendency for the low frequencies to be relatively over emphasized. This tendency is not objectionable in the original recording, but becomes undesirable in successive recordings, since it is cumulative. Fortunately, it is possible to do almost anything desired with the frequency response of the electrical portion of the system, hence it was only necessary to design an equalizer to counteract the over emphasis of the low frequencies. Due to the variation of dif- ferent records, the equalizer was made adjustable. Photographs illustrating dubbed sound tracks arc given on Figure 7. The process of dubbing two separate records together is illustrated by track 4, which was produced by combining tracks 3 and 5. The original tracks, 3 and 5, are single frequencies. A rc-rccording composed of speech and music is illustrated in track 7, being the combination of tracks 6 and 8. From an analysis of track 7, its component parts could be shown to consist of tracks 6 and 8, although with such complex sounds it is not as apparent to the eye as the dubbed track composed of two different sine waves illustrated in track 4. Track number 1 has been com- bined from two separate records of music and dialogue. This record was then re-recorded four times, track number 2 in the picture being the fifth successive re-recording. It will be noticed that successive re-recordings tend to diminish resolution, which of course affects quality. When the fifth re-recording is projected and the sound compared with the original recording, the quality is not greatly impaired. Such an experiment as this requires the ut- most care and supervision, but indicates the possibilities of re- recording. In general, although each re-recording actually in- troduces a slight loss in quality, in some cases defects in recording, such as “tubbiness” may be artificially improved. The processes outlined are in a stage of development: conse- quently the space allotted to this equipment and the type of lay- outs in the various studios are by no means uniform. It may readily be appreciated that in scoring a picture, the standard re- cording channel can be used as the pickup is by microphone, as in regular picture production, and the mixing is essentially the same. This also holds for the synchronizing operation such as adding sound effects to a completed picture. In the case of re- recording, it is desirable to adjust the volume of the output of the disc and film reproducers so that it may readily be mixed with musical accompaniment and sequences, and thence put through the regular channel. Due to the threefold function of dubbing, it is, of course, desirable to provide for utmost flexibility in the wiring scheme, as indicated to some extent in Figure 8. This, of course, applies to the signaling and motor system, as well as the transmission circuits. Each studio is providing room for dubbing equipment consist- ing of film and disc reproducing apparatus, a mixer and monitor- ing facilities. For suitable monitoring, it is necessary to surround the film reproducers, which are modified projectors, in sound- proof booths to eliminate noise from this source. In some cases one of these projectors is also arranged to throw the picture on a small screen in order to cue sound effects taken from stock records. One studio is enclosing a section of the dubbing room in sound- proof walls for microphone pickup as shown on Figure 9. For re-recording or synchronizing, the mixing is done in the dubbing room and the output of the mixer may be connected to any regular recording channel. This is being done in many cases and is only open to the objection that it ties up a regular channel which may be under a heavy production schedule. Where this is to be avoided, a separate complete recording channel is provided in the dubbing room. This usually consists of the standard amplifier equipment with one disc and one film recorder. An- other advantage is that, with all the equipment thus concentrated in the dubbing room, a smaller personnel is required for the re- recording operation. For scoring purposes, a sound-proof stage of sufficient size to accommodate a large orchestra and a variety of sound effect ap- paratus, and provided with the usual recording stage monitor and control equipment, is used. Fig. 9