Projection engineering (Jan 1932-Mar 1933)

Page 28 PROJECTION ENGINEERING CONDENSER MICROPHONE The Shure Brothers Company, 337 West Madison St., Chicago, with reference to their new condenser microphone, state: "This instrument is designed to meet the most exacting requirements for high quality radio broadcasting, sound recording, and sound measurement tests. Its outstanding characteristic is its relatively uniform response to all frequencies from 40 to 10,000 cycles. In the special design of its amplifier are combined the advantages of high output level with extreme wealth of richness in tone quality. Its reproduction is so realistic as to make it difficult for even the trained ear to discern the use of the instrument between the original source of sound and the listening ear." PHOTOCELLS Telephoto photoelectric cells for sound heads employed in talking pictures are manufactured by the Telephoto Corporation, 133-135 West 19th St., New York. These cells are made in four types to fit in all types of equipment. FILM SOUND REPRODUCER After two years of research work a new film reproducer is being announced by Acoustic Engineering Company, of Saginaw, Michigan. This reproducer reflects the designer's long experience in electrical and sound equipment design. The drive from the motor is by means of dual V belts, which method proved to be the most satisfactory after four models of direct and worm gear-driven types had been given exhaustive tests and proved less efficient. The projector drive, film drive and holdback sprocket shafts are all ground to very close tolerances and run in bronze bearings which have automatic oiling. These shafts are driven from the main drive through bronze helical spur gears which run in oil, assuring absolute quiet and smooth operation and freedom from lubrication difficulties. The film sprocket drive is filtered from the other shafts to prevent possibility of film flutter and a holdback sprocket prevents flutter from being transmitted from the takeup. The motor is optional at slight additional cost and is a specially developed slow-starting type which prevents jerking of the projector. The exciting lamp bracket is designed to be interchangeable with ease and can be prefocussed to prevent delays in sound reproduction in case of a lamp burnout. The optical system is a recent development and is capable of giving the same in tensity of light on a .0005-inch slit as is usually produced on a .001 -inch slit. The sound aperture is of the curved type preventing possibility of film buckling and giving a perfect focus at all times. Adjustable hardened and ground guide rollers of ample physical dimensions are used which permits of perfect alignment of sound track over aperture. The photo cell is of the caesium type and is mounted in a totally shielded housing so that no stray light or electrical disturbances can enter. The reproducer is adaptable to Simplex and Powers projectors. The overall dimentions of the unit are 6]/2 inches high, 10J4 long an<i 10 inches deep, which is compact and presents a clean appearance, especially so since all moving parts, except the flywheel, which also serves for a handwheel in framing, are enclosed. This reproducer may be used with any standard amplification system, but the manufacturers have developed their own amplifying unit which is completely a-c. operated and supplies P. E. cell voltage as well as current for exciting lamp and does away with the necessity of head amplifiers, thus giving a complete power and control system all in one unit, which may be placed on the front wall between two projectors. Merchandising of the above described sound system which is called super sound reproducer will be through distributors and valuable territory is still available. FULTON DIVISION OFFICE TO BE LOCATED IN SAN FRANCISCO Western Divisional headquarters for the E. E. Fulton Co. of Chicago, manufacturers and distributors of theatre equipment, under a new policy which is now being formulated by C. H. Fulton, will be located in San Francisco. Paul Bush will continue as western representative, with headquarters in San Francisco. FILM CLEANER _ The importance of keeping all motion picture films clean, particularly the sound track type, is so well understood by those in the business that it is unnecessary to advance any reasons for it. Frequently films become oily during their first run or soon after. Then they quickly go from bad to worse. The oil holds the dust and grit which grinds into the emulsion and the surface conditions become such that both the sound and screen effects are damaged. The oil and grit should be wiped off of the film as soon as it appears and before it has time to soak into the emulsion and grind into the surface. The exchanges frequently have no time to do this. It means an extra operation and when bookings are close together and the films have to be rushed out, not even the usual inspection and repair is well done. This condition can now be easily corrected. The Film Inspection Machine Co., 630 9th Avenue, New York, is marketing a theatre model film cleaner. It is designed for reels up to 15 inches diameter. This is a combination of three machines each supreme in its class. It is an enclosed, motor-driven rewinder inspection machine which detects all breaks, tears and open splices, a cleaning machine which effectively removes oil and grit from the film. Each of the above operations can be done separately or all three can be done at once at the rate of 225 feet per minute. Stops at all splices when it is desired that it should do so. A SPACING RINGS FOR CONDENSERS The Blue Seal Products Company, 260 Wyckoff St., Brooklyn, N. Y., has brought out a new spacing ring to be used with the new type cylindrical condensers. The ring is made of asbestos, and is now being used by many theatres. The use of these rings prevents the chipping and cracking frequently experienced with this type of condenser. The asbestos product used radiates heat as quickly as does the glass. The iron rings formerly used retained heat longer than glass, causing breakage due to contact between the glass and the hot iron ring after the arc was cut off. Asbestos rings are economical as frequent replacements of condensers will be avoided. ▲ ACOUSTICAL MATERIAL There has been published a new and valuable compilation of coefficients of practically all commercial materials used as interior surfaces of rooms for acoustical correction and noise abatement. More than fifty used products are considered, each type in various thicknesses. A copy of the report will be sent free by requesting same from Acoustic, room 1202, 52 Vanderbilt Ave., New York City. A WIDE ANGLE HORN The Racon Electric Co., Inc., 18 Washington Place, New York City, announces the development of a new type No. 6320 wide angle horn which is particularly adapted for sound distribution in theatres or auditoriums of extreme width — 50 feet or greater. Weighing but 60 lbs. this horn has an air column in excess of 10 feet. The bell is 76 in. by 28 in. and 37 in. deep. The throat is cast aluminum, and is self-supported on the frame. The speaker is fully covered by patents. The speaker is made of a patented nonvibratory material of sturdy construction, and is not affected by atmospheric conditions, such as heat, cold, moisture or aridity. Full details concerning this and other types of Racon air-column speakers are included in the latest Racon catalog, which will be sent upon request. A RECORD PLAYING ATTACHMENT A new portable and completely selfcontained unit for reproducing records through radio sets and power amplifiers has been announced by the Operadio Manufacturing Co., St. Charles, 111. Housed in the leatherette carrying case are an electric phonograph motor and turntable, and a sensitive electro-magnetic pickup. A carrying case in the cover provides for storage of several records without danger of breakage. Available with either high or low impedance pickup, and with 78 or 33% r.p.m. motors, for 25 or 60 cycle, 110 volt power supplies.