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1945 Theatre Catalog, 4th Edition, Page 344 (320)

1945 Theatre Catalog, 4th Edition
1945 Theatre Catalog
1945 Theatre Catalog, 4th Edition, Page 344
Page 344

1945 Theatre Catalog, 4th Edition, Page 344

way the wiring is immediately accessible

without moving the chassis from its nor mal position which is with the open side

to the front of the cabinet. The test

meter, switch and monitor volume con trol are located on a small panel on the .front of the amplifier.

The power ampliner setup of Model M-11 Dual, mounted on the rack from top to bottom, include TA-7467-A 15watt pOWer amplifier No. 1, SE-7512 amplifier switching panel, and TA-7467A 15-watt power ampliiier No. 2.

Model M-ll Dual has two TA-7457-A 15-watt power amplifiers operating in parallel to give 30 watts of power output. The switching panel supplied affords facilities for operating either amplifier alone in the event of emergency.

Model M-911 Dual has a similar rack and emergency setup, but has two Motiograph MA-7505-A power amplifiers operating in parallel to give 40-watts of power output.

Power Supply Units

In Models M-9-B, M-911 and M-911 Dual, a Motiograph built power unit, SE-7520, is utilized. This unit utilizes two of the new highly efiicient mercury vapor rectifier tubes. The chassis type design is similar to that of the Western Electric power amplifier resulting in exceptionally easy installation, good accessibility and adequate ventilation.

In Models M-ll and M-11 Dual the Western Electric built TA-7471 power unit is utilized. This unit is designed for extreme reliability of operation and low maintenance cost. Western Electric 288-A vacuum tube rectifiers are used and the filtering is such as to give the pure d.c. required for highest quality sound system performance. The vacuum tube sockets are so arranged as to permit instantaneous. change of tubes. A special ballast lamp effectively maintains the exciter lamp current constant regardless of line voltage changes.

Mirrophonic De Luxe SH 7500

The Mirrophonic de luxe reproducer is standard in the Motiograph-Mirrophonic line.

Among the important features is the use of only one large precision machined 32-toothed sprocket which runs at half the speed of the conventional sound head sprocket. The lesser r.p.m. of this sprocket tends to pull the film over the stabilizer evenly, giving smoother action, eliminating possible film vibration and providing protection against flutter. This single sprocket makes for extreme simplicity of threading and results in an exceptionally roomy sound head.

The impedance roller is designed to give proper compliance of the film around the stabilizer drum under all conditions of film shrinkage.

The rotary stabilizer, with its enclosed flywheel operating in a specially developed liquid, imparts to the travel of the film a remarkabe steadiness and results in a fiutter content well below any other reproducer available.

The sprocket and guide roller, the shafts and the four sturdy extra-wide gears are machined with exacting precision of workmanship. All shafts operate on ball-bearings. This assures long life and the acme of silent operation so necessary to the reproduction of true, living sound.

The constant speed direct-drive motor is mounted in a central position on one side of the reproducer and regardless of the projection angle, the drive shaft operates horizontally. Because the motor fits snugly on a rigid table against the side of the reproducer and near the natural center of gravity of the projector, the entire assembly is stable, proper lubrication Without leakage is assured and no thrust bearings are required.

The sidemount also permits connecting the motor to the reproducer through a simple flexible coupling. A silent link chain couples the reproducer and the


projector mechanism. The chain drive isolates the intermittent action of the projector mechanism from the reproducer, thus giving the maximum of stability and smooth, quiet operation.

The design of the motor offers protection against excessive motor current occasioned by abnormal or mechanical overload line voltage through an "overload sentry" which automatically functions as a circuit breaker when needed. The starting time of the motor is such as to conform to the recommendations of the Academy of Motion Picture Arts and Sciences for motion picture projector service.

Loudspeaker Equipment

The loudspeaker system furnished in Model M-9-B is especially designed and consists of:

(1) High frequency 5-cell multi-cell ular horn

(1) Electro-dynamic high frequency


(1) Electro--dynamic 18" low fre quency unit

(1) Baffle and bass-reflex cabinet

(1) Crossover filter network with ad justable high frequency channel attenuator

(1) Monitor speaker.

The multi-cellular horn is rigidly constructed of ca t metal alloy and is designed and built so that with only nve primary cells, performance equivalent to a lZ-cell assembly is achieved. The horn efficiently distrfbutes high frequency sound energy over a solid angle 90

degrees horizontally and 45 degrees ver- ,


The electro-dynamic high frequency unit is of the metal alloy diaphragm, sound chamber type. It employs a small rugged narrow annular type diaphragm much stiffer than the more conventional spherical or dome type diaphragm. Speech reproduction is crisp and clear without having a hard or metallic quality. The whole unit is ruggedly constructed and designed for maximum life expectancy. This unit has given such extreme satisfaction in the field, it is used in varying numbers in all Motiograph-Microphonic models including the most costly.

The electro-dynamic 18-inch low-frequency unit is particularly designed for operation with the associated equipment andtis the most highly efiicient low frequency speaker available.

The low frequency baffle consists of a ruggedly constructed cabinet containing the electro-dynamic 18-inch low-frequency unit. The design of this cabinet incorporates the famous bass-reflex principle. Large vxings asiociated with the cabinet further improve the low frequency response characteristics of the combination.

The loudspeaker system furnished in Models M-ll, M-11 Dual, M-911 and M-911 Dual is especially designed for the medium sized theatre and consists of: one high-frequency 32-cell multi-cellular horn with 90-degree horizontal and 45 degree Vertical coverage, one electrodynamic high frequency unit, two electromlynamic 15-inch low-frequency units, one folded horn, one crossover filter network with adjusiable high frequency channel attenuator for mounting inside low frequency folded horn on stage, and one monitor speaker. (In models M-911

1945 Theatre Catalog, 4th Edition, Page 344