Projection engineering (Jan-Dec 1931)

Page 32 PROJECTION ENGINEERING KEASBEY & MATTISON MARKETS SOUND SCREEN A new sound screen marketed under the trade name of "Visibestone," consisting of a series of rod-like filaments, the shape and angles being based upon complicated mathematical formulae, has been introduced by the Keasbey & Mattison Co., asbestos manufacturers of Ambler, Pa. While complete stereoscopic vision is not claimed for this new screen, the rodlike texture of the Visibestone screen is said to lend unusual depth to the projected picture, while the scientifically compounded mesh permits greater and more even sound filtration. It is also pointed out by the manufacturer that the new screen very definitely corrects distortion of both sight and sound. This correction is attributed to the special weaving and rodlike texture of the screen. Light is evenly reflected from the round surfaces of the asbestos threads into the remote angles of the auditorium. Being basically fireproof, the liability of fire and consequent panic in the theater is greatly reduced, since there is nothing in the Visibestone screen to ignite or smoulder and give off poisonous fumes or noxious gases to alarm the audience, the company declares. A CARBIDE AND CARBON VINYLITE RESIN USED IN NEW VITROLAC PHONOGRAPH RECORD Union Carbide and Carbon Corporation through its subsidiary, Carbide and Carbon Chemicals Corporation, has entered into a contract to supply RCA-Victor large quantities of Vinylite resin to be used in molding the new Vitrolac records, which will play several times as long as the old type of record. The unusual physical properties of Vinylite give many favorable features to the record, particularly toughness, flexibility, thinness. The absence of contraction or shrinkage when Vinylite is molded, it is stated, results in an unusually accurate reproduction of sound or music, including even the overtones of the high notes of a violin, with practically no surface noises. These characteristics have made it possible for RCA-Victor to design an entirely new type of record which will last three times as long as the old type record of the same diameter, and the surface of which contains twice as many sound producing grooves as the old type of record. ▲ RACON IMPROVEMENTS Racon Electric Co., Inc., pioneer manufacturers of units, horns and sound equipment, announce improvements in their units, giving more powerful and more perfect response as well as increased efficiency. They also announce a reduction in prices on their complete line. A A NEW FILM CLEANING DEVICE In the near future, The Blue Seal Products Co., 260 Wyckoff St., Brooklyn, N. Y., will have ready for the market a newly designed film cleaning device for Simplex projectors. This device removes oil and dust from the film while it passes from one magazine to the other and also has an automatic valve which, in the event of fire taking place at the aperture, releases a specially prepared liquid instantly at the aperture. This device has been on test in several of the largest metropolitan theatres for several months. It has met with unqualified approval from everyone who has operated it. (This news ties up with the story regarding the S.M.P.E. Projection Practice Committee's remarks on the subject of "protecting positive film," which will appear in the January issue of Projection Engineering.) The liquid not only has cleaning properties but also acts as an emulsion preservative and prevents buckling as well as eliminating the possibility of new emulsion coating the tension shoes, a factor that caused many film fires in the past. NEW PORTABLE SOUND EQUIPMENT The Webster Company, 850 Blackhawk Street, Chicago, 111., announces a new portable outfit for sound transmission. The highlights of this portable are extreme compactness. The entire equipment, including speaker, phonograph and microphone, occupy a space slightly larger than one cubic foot. The tube arrangement is one 224 and two 247's, using a 280 for full-wave rectification ; the weight being under forty pounds. Provision is made for mixing the output of the microphone and the phonograph together. Interconnecting cables are provided with polarized plugs to facilitate connection. The entire assembly is made in an attractive and substantial portable case. A BELL & HOWELL FIVE-WAY SOUND PRINTING ATTACHMENT The Bell & Howell Company is making an alternative sound printing attachment which can be fitted to their Model D continuous 35 mm. printer. Instead of having movable masks at the aperture, the five-way attachment utilizes a 220° drum in which are cut five openings. Four of the openings are arranged to take care of printing the sound and picture areas re Five apertures cut in a 220° drum and indexed to facilitate operation by registering correct aperture for sound or picture printing. (A) The drum, in which are cut five openings— one full aperture, one each for sound and picture printing for operating the negative forward or reverse (A3) Sound aperture — reverse run; (A4) Picture aperture — forward run; (AS) Sound aperture — forward run; (C-l-2-3-4-5) Index dial; (D) Lever and pin which move drum to opening indicated, on Index dial. spectively of the negative, whether the negative is running forward or backward. The fifth opening is arranged to print ordinary "silent" negatives. In other words, instead of arranging masks tc give the various combinations of aperture openings, the five-way wheel is turned to the correct openings. These openings are indexed to facilitate the operator using them for sound and picture area printing, in correct sequence. A ELECTRODYNAMIC UNIT An electrodynamic speaker has been brought out by the Fox Engineering Com pany of Toledo, O., for use in theatre sound and public-address systems. A particularly interesting feature of this unit is an interchangeable "voice coil cartridge," which may be removed for the purpose of substituting a new one (instead of purchasing an entirely new unit) by merely removing one "master" screw. The outer bowl is stamped from one piece of heavy alloy. In this bowl rests the "field coil" for supplying the magnetic energy. This energy, which is of six volts, can be supplied by either an ordinary 6volt storage battery, or a specially designed dry rectifier also made by the Fox concern. ALUMINUM HORN OFFERS NEW ADVANTAGES The first size in a full series of all-metal trumpet horns has just been offered the sound projection trade by the Fox Engineering Company, Toledo, manufacturers of horns and high-powered electro-dynamic units. While the tone characteristics and physical requirements of the perfect amplifying horn have long been recognized by sound engineers, the actual attainment of these characteristics has been a matter of slow and painstaking development. Allmetal horns are not new, but an all-metal horn that is entirely free from rasping and vibration noises is an achievement that will be welcomed by every sound engineer in the country. This new Fox horn, of conventional trumpet design, has consistently shown, under all conditions, a clear, bell-like tone that has surprised and pleased every engineer that has tested it. Notwithstanding the fact that these horns are 6 ft. long, and have a bell diameter of 32 inches, they are of spun aluminum and free from lateral joints or seams. This construction makes possible a definite radial uniformity that accoutns for its fine tone. Aluminum is not only an ideal medium from the standpoint of resonance. It is easy to set up and take down for temporary use, and when knocked-down into its two integral parts, is extremely easy to store and ship. These horns are entirely free from the influence of atmospheric and moisture conditions and are almost indestructible in normal use. Weight is only 12 pounds. NEW S. O. S. SOUND-ON-FILM AMPLIFIER After many months of experiments, S. O. S. engineers have developed a sound-onfilm amplifier which totally eliminates all batteries, chargers, rectifiers motur-generators, and complicated wiring. Proper unified amplification has been a problem with many theatres wishing to install sound-onfilm reproduction, but with the advent of the new S. O. S. unit, the most pleasing results are now possible with a minimum of expense and an extremely simple installation. Among the outstanding features of the S. O. S. unit are all a-c. electric operation, photocell balancers, volume fader control, changeover switch, jewelled indicators, direct current meter, master a-c. switch, real high-frequencies, junction box outlets, no messy batteries, 4-stage amplification, built-in P. E. C. amplifier supplies exciter current, non-sync input jack, shielded photocell leads, exciter lamp ammeter, easily accessible, simple to service, matched impedance for any sound head or speaker.