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1954-55 Theatre Catalog, 12th Edition, Page 286 (250)

1954-55 Theatre Catalog, 12th Edition
1954-55 Theatre Catalog
1954-55 Theatre Catalog, 12th Edition, Page 286
Page 286

1954-55 Theatre Catalog, 12th Edition, Page 286

all of these variations electrically with sufficiently complex equipment, but it must be realized that the curves shown represent only one movement path. For example, at C are shown four possible paths. One maintains constant arrival time difference Tmr; one constant inten I . sity ratio in: Lfti

ant to direct sound ratio R/D; and one constant quality Q. In each case the other three factors vary in a different way and diderent from the curves of B. Thus it will require considerable skill and judgment from the mixer. When conditions can be arranged for stereophonic pickup the relationships take care of themselves.

The pseudo-stereophonic effect is limited to non-simultaneous single sources, because all sounds recorded by the single microphone will be localized at the same place for any one setting of the controls. Thus an individual set of controls and an individual recording is required for each sound which must overlap another. A multiple channel stereophonic system is necessary to record a spread source such as an orchestra, restaurant scene, a chase, or a battle, if positional illusion is to be obtained. However, on such a background, dialogue or sound effects can be

; one constant reverber effectively superimposed by manual control. In the writers opinion the pseudostereophonic techniques will serve an important and continuing auxiliary function in picture production, but will not be found an acceptable substitute for

stereophonic pickup.

Theatre Problems

From the standpoint of the exhibitors view of stereophonic sound, there appear to be two items of particular interest. The first concerns more adequate coverage of the whole audience area. This is discussed in the paper under ffEffect of Observer Shiftft Even if a studio does a superlative job of stereophony for the central seats, the illusion will be less satisfying, or even unsatisfactory, for side seats. Something can be done about this by proper pickup methods which the studios are learning, but it should also be attacked from the theatre standpoint. Suggested remedies are discussed briefiy under ffMethods of Reducing Shift," but apparently very little fundamental investigation in this field has been carried out. This is probably because the studios have been engrossed in their pressing production problems since stereophonic sound became of commercial value. Considering its serious import to theatre owners, it appears that

THIS IS a photograph'showing the redesigned system for the EHPI in 1941. If was used in many experiments and demonstraqu by the ERPI, and is a symbol of the progress made in stereophonic sound.


they should actively support the start of a program to study this effect as soon as possible. It seems probable that much improvement may be expected over present coverage when new techniques are developed.

The second subject concerns the various systems for switching or controlling loudspeaker output from a single sound track on the film, which are being installed in theatres in place of true sterephonic systems. These are used both to save expense and to obviate present technical difiiculties of multi-track release prints. The writer feels that, as in the past, the technical difficulties are transitory and will be eliminated in the course of a reasonable time. Presumably the exhibitor feels that sound movement is valuable in his theatre, or nothing in addition to the monophonic system would be installed. The use of such systems, therefore, depends upon economic judgment and any possible advangtages from a fundamental standpoint.

These systems, from the functional standpoint, are just pseudo-stereophonic systems with the pan-pot moved into the theatre and operated by a robot dubbing mixer. The simplification results from the fact that a robot moves relatively slowly, and a very elementary channel, compared to a sound track, will satisfy his needs. A switched or controlled system actually has 4 channels --the high fidelity sound track, plus 3 channels of information which must be separated to tell the robot which loudspeaker to connect, or how to adjust the relative amplifier gains.

These systems can therefore be expected to do what the purely pan-pot technique in dubbing can do. If only one loudspeaker is turned on at one time, as in a switched system, sound will definitely be localized at that position, but the only possible positions are those of the loudspeakers. If relative levels are adjusted by sub- or superaudible pilot tones, intermediate positions are possible, subject to the limitations described above for panpot technique.

It is imperative to remember that, since there is only one sound track, all sounds will come from the same direction. Thus background music or crowd noise will shift position as dialog or sound effects shift. If one moves, the other must, and as an actor walks across the stage the orchestra goes with him. No stereophonic quality of spaciousness can be preserved; to spread out an orchestra requires true stereophonic reproduction. Some benefit in musical reproduction seems to be obtained from connecting multiple loudspeakers with different relative bass and treble response to a single channel, as long as conditions remain constant. However, with a single sound track, dialogue and music are inseparable, and either everything moves, or they are left stationary, in which case a control system is not needed. It is not possible, as in the studio, to combine the controlled dialog with a spread orchestra because of the single sound track. It thus appears that the switched or controlled system has no functional advantages over the stereophonic system, and must be justified only by its economy.

1954-55 Theatre Catalog, 12th Edition, Page 286