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1945 Theatre Catalog, 4th Edition, Page 504 (478)

1945 Theatre Catalog, 4th Edition
1945 Theatre Catalog
1945 Theatre Catalog, 4th Edition, Page 504
Page 504

1945 Theatre Catalog, 4th Edition, Page 504

quality of its sound reproduction. As the result of experience with many installations a great deal has been learned about the types of sound systems which provide ilie most satisfactory results.

There are four general types of sound reproducing equipment in use in drivein theatres: (1) the in-car type of loudspeaker, where an individual portable unit is provided for each car, (2) the now obsolete underground type of loudspeaker unit which is permanently installed in a suitable concrete housing- underground. Such speakers supply tWO cars with sound through a metal grille which is mounted flush with the ground, (8) the aboveground type of loudspeaker system, where each unit is permanently installed in a weather-proof bafiie mounted either on a pipe or post several feet above the ground and intended to supply two cars, (4) the central stage-type of loudspeaker system, where the components are centralized at the screen and serve as a single sound source to cover the entire area.

Those portions of the sound reproducing system which are located in the projection building are identical to those which are utilized in large theatres. Sound reproducers are identical, although in most of them more powerful ampliders are employed in order to obtain the increased power that is necessary. Some sound systems have been powered with as little as 30 watts, though far better results are obtained with powers of 100 or more watts.

Some sound systems are also utilized with separate power amplifiers for each group of 50 speakers. In such cases a number of power amplifiers are required, but unless the theatre area is filled with cars, there is no necessity to utilize all of the power amplifiers, as the ushers can spot the car in front of the speakers which are powered. As the lot fills up, additional power amplifiers and additional groups of speakers are put into use.

Up to the present time, there have been five general 'types of individual speakers used. These can be classified ins to (1) those permanently mounted beside

lNSTALlATION OF THE CONNECTION BOX, SPEAKERS, AND SPEAKER SUPPORTS is shown in this Radio Corporation of America drawing. These items are furnished by the company, but the customer provides the 4x4-inch wood post or the 2-inch pipe in which the equipment is mounted. Besides showing the critical measure.


the car, and (2) those which can be taken inside the car, commonly called in-car speakers.

There have been three types of peiu manently mounted speakers: (1) permanently mounted on bulkhead in front of car, (2) permanently set in the ground between cars and covered with a metal grille, and (3) permanently mounted on a pillar beside the car window.


In order that the reasons for the use of the speakers recommended today may be fully appreciated, some of the speaker designs and sound distribution methods used in the past will be brieiiy discussed.

The centralized speaker system used in the first five drive-in theatres. It consisted of wooded directional horns and dynamic cone-type speaker mechanisms, similar to those used in enclosed theatres at the time. In order to cover the parking area with sound, it was necessary to operate these speakers at their full capacity, and this resulted in frequent speaker failures. In addition, considerable trouble was experienced with sound escaping outside the theatre lot. People residing close by to the theatre complained bitterly and in many cases, theatre owners were served with injunctions and attempts were made to close their theatres.

It is evident, therefore, that a new speaker system would have to be devised for drive-in theatres. The most obvious, and the simplest solution at the time, was the use of a small speaker and bafHe installed along each ramp directly in front of the car. As a matter of economy, one speaker unit was mounted so that it would serve two cars. At about the same time, experiments were conducted with small speakers installed underground, adjacent to the parking positions.

The use of individual speaker units permanently installed along the ramps did not entirely prevent the sound from escaping to surrounding areas. Considerable trouble was also experienced with speaker failures, because the first units were not 100 percent weather-proof. In addition, it was still diiiicult. to hear com over the car in front.




fortably during cold or rainy weather when the customers closed the car win(lows.

In the stage type of loudspeaker system, the necessary acoustic power is transmitted from what is essentially a single source at or near the screen.

Since this single source is intended to supply sound to the entire theatre area, it is apparent that this concentration of energy may involve serious disturbance problems to neighborhoods immediately surrounding the theatre location. Indeed, in some localities this form of sound distribution is prohibited by local authorities. It is recommended that this aspect be investigated in every case before serious consideration is given to its adoption.

This type of distribution offers marked and obvious advantages in the way of low initial equipment cost, lower wiring and installation cost, and reduced maintenance expenses. Where it proves practicable, therefore, this type of system is preferable. Such a system would include high and low frequency units, multicellular high frequency cellular horns, folded horns, and a dividing network.

As the theatre area to be served is large, it is obvious that the speaker system must have more components than those existant in the average indoor theatre. A combination of four high frequency units, eight low frequency units, two folded horns, and two multi-cellular metal horns would be adequate for even the largest drive-in theatre.

If a sound screen is employed, the badies can be mounted behind the screen. The use of a sound screen requires protection facilities, however, during periods when the theatre is not in use; therefore, in mOst cases the screen consists of suitable white-painted building board, or tin, backed with wood, and in instances the loudspeaker bathles must be mounted above, below, or at the sides of the screen.

There were several disadvantages inherent in the centralized speaker system. During rainy or cold weather, when it became necessary to keep the car windows closed, it was extremely difficult for the patrons to hear plainly even

ments in the installation of this equipment, the drawing also shows some of the characteristics of the modern graded ramp, through the use of which the Forward part of the automobile is raised sufficiently that all occupants will be able to see Speakers for two cars are mounted on each standard.


1945 Theatre Catalog, 4th Edition, Page 504