The Film Daily (1931)

THE Sunday, July 19, 1931 i^^ DAILV e:quipment © BOOTH Monitor Horn Volume and Other Problems Discussed by Expert The following is by R. H. McCullough, Fox Theaters sound expert, whose discussions of equipment problems appear regularly in Fox's "The Last Word." j With every sound installation there iiS a monitor horn installed in the protection room, so that the projectionist Tiay hear the sound as well as the auilience. The volume of sound from he monitor horn must be kept at a |;ertain level, so that the sound cannot |)e heard in the theater auditorium. |\ loud monitor horn will produce an jXho in the rear of the auditorium (f the projection room is not sound ;)roof. I have found that excessive circumTerences play-in in the intermittent :novement will result in a slight lack if synchronism with movietone repror Ouction. There is a very exact relaI lion between the projector aperture I j.nd the sound gate registration. Un1 less it is very bad this probably will t 'lot amount to very much, insofar as |i t has to do with the screen effect. I .^he projector mechanism intermittent J jaovement must be 100 per cent perj ,ect, as every little fault eliminated i lelps toward perfection. f The loud-speaker unit is a delicate iece of mechanism which should not i 'e subjected to avoidable shocks. When I iie speaker units are moved from one " 'lace to another, those who handle { !hem should be duly impressed with I he importance of being careful. It is quite evident that if hum is en ;i vountered with both Movietone and '[ fitaphone subjects, the trouble is in ) be power amplifiers. Hum can often j .€ traced to defective sliorted vacuum I jibes, either in the stages preceding 1 ie last stage or in the last stage it ' i If. Unbalanced rectifier tubes will • luse a very bad hum. Worn out . ibes (low emission) frequently cause 'I ijUealing and howling. If popping or ! rackling noises are perceptible at high Dlume levels, this trouble can often be icated in the base of one of the 211 vacuum tubes in the 43-A amplifier " one of the 205-D vacuum tubes in le 42-A amplifier. The first point to remember is to iieck the tubes and take nothing for j'anted. Excessive hum can be caused 'f' shorted by-pass condensers, open ■ condary to input transformers and 'as resistors, shorted filter chockes ;id filter condensers although the latr condition will manifest itself in •erheating of the rectifier tubes and ower transformer. Great care must I l exercised that the input wiring to the amplifiers is well shielded from all A.C. wiring. Occasional band hum can sometimes be traced to the fields from adjacent electrical equipment, such as mercury arc rectifiers, rotary converters, motor generator sets and small motors. The A.C. circuit, which feeds the power amplifiers and rectifiers, should always be run independently and should never be on the same circuit with any other electrical appliance. The best method to find out definitely if the hum is caused by some other electrical appliance is to turn on the amplifiers with all the other electrical equipment turned off and if you find that the hum is not in the amplifiers, turn on each electrical appliance individually until you find the one which is causing the frequency hum during the time the amplifiers are in operation. Pointers and Suggestions NATl BUSY INSTALLING CHAIRS AND CARPETS Many theater owners throughout the country are currently improving their houses with new chairs and carpet installations, according to an announcement made by the National Theater Supply Co. Among those equipped with new chairs include the Loma, Burbank, Calif.; Delft, Marquette, Mich.; State, Salem, O. ; and the Majestic, Reno, Nev. Recent chair installations announced by the company include the Zenith, Davenport, Iowa ; Grand, Perry, Iowa ; Sun, Grand Lodge, Mich. ; Taft, Chillicothe, Mo.; New, Mullins, S. C; Home, Blytheville, Ark., and the Ritz, Daytona Beach, Fla. Low-Priced Recording System Los Angeles — A new low-priced studio sound system known as the "Rico," employing the double system of recording and in which has been incorporated the new method of noiseless recording, besides having been especially designed for use in all climates, has been marketed by the Radio Installation Co. of this city. The new equipment, engineers of the company claim, is an effort to meet the needs of independent and foreign production companies which cannot afford the higher priced sound equipments. J^EEPING the theater ventilated ' with clean, fresh air during the summer months, especially where no cooling and ventilating plant is employed, is most essential. In cases where janitors are doing cleaning in the daytime, it could be arranged to have them come on shift immediately after the show is out at night. This will allow them to open the house wide open and take advantage of the fresh, clean, night air to dissipate the heat inside the theater and cool it off for the following day. This plan, if practiced regularly, will produce surprising results. * * * Your many mechanical devices operating in your theater may be running, but, are they operating at full efficiency? One day each week set aside for inspection and the checking of all mechanical equipment, including the ventilating system, will go a long way toward keeping your equipment operating at full efficiency. * * * Careful attention should be paid when oiling projection equipment! Regular and frequent lubrication has a direct relation to the life of the projector mechanism. Oil should be sparingly applied to bearings and any excess wiped off before projecting film. Absorbent pads, changed frequently, will prevent oil soaking into the film amplifier and causing damage to insulation of wires, and also prevent the accumulation of oil on the film. Adaptor for Test Set An adaptor that will permit 50Watt, type 211-E tubes, to be checked quickly and easily, and which may be used with either the company's model 565 or 566 test sets for theaters, has been designed and is being put out by the Weston Electrical Instrument Corp., of Newark, N. J. Smoking Tray Give-aways All-metal novelty smoking trays in unique designs that can readily be adopted as a give-away for building up theater patronage are being marketed by the Precision Metals Workers of Chicago. Draperies Decorations Magnascope Screens 340 W. 41 si St. Settings Acoustical Treatments Acoustical Banners New York City COLORED HOOD TOR LAMPS SERVES DOUBLE PURPOSE Chicago — A special, natural colored glass hood for placing over white lamps to eliminate bugs, insects, 'mosquitoes, etc., besides serving to make the theater more attractive, has been developed by the Reynolds Electric Co. of this city. In addition to eliminating night insects from hovering about the lamps, the Reco color hoods give a pleasing, cool green or amber light that heightens the attractiveness of the theater. The hoods are being offered in sizes to fit over white lamps from 10 to 60 watts. For 75 watt to 500 watt lamps, Laco color hoods of the same material are used. For floodlights, etc., color plates are manufactured by the company. Installs New Cooling System Milwaukee— .A. $50,000 refrigerating plant has been installed in Universal's Alhambra. Fred S. Meyer, president of the M.P.T.O. of Wisconsin, is managing director of the house, which also has undergone other improvements. Portable Public Address System A compact portable public address system known as the Amplion Portovox, consisting of an Amplion unit, exponential horn, amplifier and microphone, and which can be packed m two small packages for transportation, has been put out by the Amplion Products Corp. of New York. Sono Corp. Joins United Aircraft Pittsburgh — Sono Equipment Corp., manufacturers of Sonofilm sound devices, is now connected with United Aircraft Corp. of America, F. H. Healy general manager announces. Fred Solomon is local representative of the A. C. or battery type equipment manufactured by the company. JUST AROUND THE CORNER from every American theatre NATIONAL THEATRE = SUPPLY COMPANY i Branches tn nit Pri77cipal Cities 1