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1948-49 Theatre Catalog, 7th Edition, Page 257 (246)

1948-49 Theatre Catalog, 7th Edition
1948-49 Theatre Catalog
1948-49 Theatre Catalog, 7th Edition, Page 257
Page 257

1948-49 Theatre Catalog, 7th Edition, Page 257

more durable material than an ordinary pressed paper gasket.

Weatherproofing has been successfully built into all parts of the Mobiltone speaker. Housing of the entire unit utilizes deep drawn, die stamped sheet aluminumeanodized by a special process which etches into the aluminum a tough, synthetic oxide film ten-thousandths of an inch thick. This thin layer shuts out completely all ordinary corrosive elements present in the atmosphere. All joints are fastened with aluminum rivets except in two places where stainless steel screws are specified. However, the use of stainless steel prevents bi-metallic corrosion and the entire unit presents a continuous corrosion-proof surface with an enduring lustrous finish.

By mounting the volume control on the side of the speaker and allowing only a small part of its circumference to protrude, the manufacturers have attempted to forestall damage from both vandalism and ordinary rough usage. Other special features include: a slipover flange on the bottom of the junction box which is adjustable to any pipe from 1% inches to 2 inches and which eliminates the necessity for threading the pipe; the hanger brackets for placing the speaker unit in the car, which are rubber coated and equipped with a rubber bumper on the bottom of the speaker to eliminate damage; a built-in parking light, standard with each unit which can be focused from spot to flood; and a 12-foot coiled cord lead on each speaker.

The confidence of both Theatrecraft and General Electric in the efficiency and ruggedness of the 514 inch speaker cone has led to a guarantee of this unit by both companies.

Another Mobiltone model scheduled for installation in a North Carolina drive-in in the latter part of 1948 includes all the above standard features with one exceptionethe speaker for this model is a 4 inch General Electric all weather cone. Reason for the smaller speaker is the incorporation of a heater unit in the top portion of the speaker case above the speaker cone. This heater, also made by General Electric, is of calrod incanel construction and is said to be waterproof. The entire heater unit is encased in a ceramic material which eliminates the conduction of heat to the speaker cone. A fan is mounted behind the unit to project the generated heat into the automobile. The heater is operated by a switch on the side of the case opposite the potentiometer. The Koiled Kord running from the junction box to the speaker is twelve feet in length and carries three heavy-duty conductors.

1948 MOBILTONE CENSUS: Approximately 48 installations.


Motiographis in-car speaker, a cire cular model with perforations in the front, is sturdily constructed to survive rough handling from Tarzan-inspired drive-in patrons. Yet it is said to be easy to handle and pleasing in appearance. For effective protection against the weather, the speaker unit itself is weatherproofed by a special process

MOTIOGRRPH speaker with concession signal.

while the steel housing is bonderized (phosphate coated) for ideal paint adhesion and then finished in baked enamel or brushed cadmium. For automob1le protection, the speaker hooks are rubher-plated.

The speaker unit, utilizing a 5 inch cone, is designed with large mechanical and electrical safety factors. Efficiency and ruggedness are obtained through the use of welded magnetic structures and heavy duty Alnico-5 permanent magnets. Individual speaker volume controls are of the constant impedance type, and amplifier loading, therefore, remains the same independent of control settings. This factor is said to insure optimum amplifier performance and to eliminate the need for constant readjustments if there are changes in the number of speakers in use. Controls are supported by brass splash screens and are therefore cushioned against mechanical damage; control knobs are machined from solid aluminum for strength and appearance.

For ease of installation and speed in changing speakers, the speaker cables are provided with spade terminal lugs. The speakers are quickly disassembled if the need arises, but the use of patented screws discourages curious patrons from taking them apart with a coin, knife, or ordinary screw driver. The brass splash screen immediately behind the perforated front of the speaker housing is designed to prevent damage to the speaker unit from the insertion of foreign objects. This splash screen also is said to keep insects and driving rain from reaching the speaker unit cone.

Motiograph in-car speakers are available with plain rubber-covered cables and a companion steel cable covered with a waterproof casing.

Motiograph's j u n c t i o n boxes are equipped with a special pipe flange which permits them to be fastened to a wooden post or used on unthreaded pipe with an outside diameter of 2" to 31/2". The SE7545 model is made from two strong and bright aluminum castings and the manufacturer claims that it is completely corrosion-proof, requiring no periodic

painting to maintain its pleasing appearance. V

The top casting covers the impedance matching transformer and terminal block for the speaker and feed cables. The lower base casting fits the post support and has two integral speaker hooks which are said to allow easy replacement of the speakers after use. This speaker hook location is said to permit ready access for servicing of the trans former, terminal block and speaker, and feed cables without the necessity for dropping the speakers on the ground. The two castings of the junction box are joined tightly together by two strong, readily accessible bolts, making a weatherproof enclosure for the transformer and terminal block. It is said that the electrical circuits of the box are so arranged as to prevent accidental short circuits in speaker cables from affecting other junction boxes on the same ramp feed circuit.

To provide for a lighted speaker post area and a means of signaling a concession attendant Motiograph furnishes a version of its junction box with a white light to shine down upon the junction box support and also a red light to signal the car hop. The post lights are operated from the projection building, while the concession lights are turned on and off by the car occupant who operates a push-button switch on the speaker for either continuous or intermittent lighting.

A single un-insulated bare copper wire to each box position, in addition to the usual two-conductor insulated parkway cable, is sufficient. The amount of light produced by the base and signal lights is entirely sufficient for their purpose, but not enough to cause objectionable glare. The relatively low lamp supply voltage meets the safety requirements of the National Electrical Code without any necessity for expensive separate standard voltage lighting circuits to each box position.

Special features claimed by the manufacturer for this junction box include: an impedance matching transformer fully impregnated against moisture so that rain, condensation, or early morning fogs do not make the transformer inoperative; patented line terminal lugs into which the straight, skinned ends of the ramp feed cables can be locked in a matter of seconds.

1948 MOTIOGRAPH CENSUS: (N0 installation totals supplied).


RCAis in-car speaker has been placed in a new housing designed by John Vassos, the nationally known stylist, for extra Visual appeal and greater ease of handling; and a new speaker neck insures immediate and fool-proof attachment in the car.

After extensive acoustic tests, a 4-inch speaker mechanism was chosen for the RCA equipment since it gave the best performance within an enclosure of convenient size. It is a recognized fact that the low-frequency sensitivity of an enclosed-type speaker is a function of the size of the enclosure, as well as the size, mass, and stiffness of the diaphragm.


1948-49 Theatre Catalog, 7th Edition, Page 257