Projection engineering (Jan 1932-Mar 1933)

FEBRUARY, 1932 Page 25 mixer panel should never exceed four individual sections. Output Control The control of the output of an amplification system is as necessary as proper input control. To obtain the best results, an individual control of speakers is essential. The number of speakers which can be successfully operated from an amplifier of certain size and power output, depends on the manufacturer's rating. The output of the majority of commercial amplifiers is provided with impedance adjusting transformers to meet the requirements of multiple speaker output. Dynamic speakers for use on high power equipment eliminate the usual transformer and depend on a direct connection to the voice coil from the line. The impedance of dynamic voice coils vary with each manufacturer of speakers. The range extends from 2 ohms to 20 ohms. However, the majority of speakers have a voice coil impedance between 10 and 15 ohms. Fig. 5 illustrates the individual control of three dynamic speakers connected in series. The speakers are from 10 to 15 ohms, and the total impedance of the group is 30 to 45 ohms, and should be fed from a line of the same impedance value. A proper control for each speaker is "L" pad No. 94-001 rated at 10 watts for use with amplifiers of high power output, or "L" pad No. 96-001 rated at 4 watts for use with amplifiers of moderate power output. It is possible to connect dynamic Fig. 5. speakers in multiple by series and parallel connections to obtain any desired impedance value. Thus, for a multipleconnection of four dynamics of 10 ohms each, parallel two sets of two each and then connect the two sets in series, the resulting total impedance value is 10 ohms. If all four were connected in series the total impedance would be 40 ohms, while if all four were parallel the result would be 2y2 ohms. AAA HEARINGS IN MARCH ON PATENT SUITS COVERING TALKING PICTURES AND RADIO TEN suits involving the motion picture and radio industries listed in the United States district court at Wilmington, Del., before Judge John P. Nields in the December term were continued until the next term in March. The suits continued are : Western Electric Company, Inc., Electrical Research Products, Inc., and American Telephone and Telegraph Company against the Stanley Company of America. De Forest Radio Company against the Duovac Radio Tube Corporation. The suit may be dismissed. United States of America, represented by L. E. Wales, United States Attorney, against Radio Corporation of America, General Electric Company, American Telephone and Telegraph Company, Inc., Westinghouse Electric and Manufacturing Company, RCA Photophone, Inc., RCA Radiotron Company, Inc., RCA Victor Company, Inc., General Motors Radio Corporation and General Motors Corporation. American Tri-Ergon Corporation, Tri-Ergon Holding A. G., Josef Engl, Joseph Massolle and Hans Vogt against General Talking Pictures Corporation, DeForest Phonofilms, Inc., and Lee DeForest. Joseph Lopiano and Henry Frank, Jr., receiver of American Reproducer Corporation, against Pilot Radio & Tube Corporation. General Talking Pictures Corporation and DeForest Phonofilms, Inc., against RCA Photophone, Inc. General Talking Pictures Corporation and DeForest Phonofilms, Inc., against RKO Radio-Pictures, Inc. John M. Miller against National Broadcasting Company, Inc. John M. Miller against RCA Communications, Inc. The suits of General Talking Pictures Corporation and DeForest Phonofilms, Inc., vs. RCA Photophone, Inc., and General Talking Pictures Corporation and DeForest Phonofilms, Inc., vs. RKO Radio Pictures, Inc., may be tried in February. A DR. GOLDSMITH FAVORS AID FOR PROJECTIONISTS THE work of the projection practice committee of the Society of Motion Picture Engineers, when completed, will be a valuable contribution to the motion picture industry, according to Dr. A. N. Goldsmith, president of the society. "When I recall that the driver of a five hundred dollar automobile has at his command an oil gauge, a speedometer, an ammeter, a radiator thermometer, and what not, with which to 'feel the pulse and take the temperature' of the machine continuously while operating it, I look with astonishment and sympathy at the projectionist, who is obliged to project pictures night after night before a one thousand box office house, in a two-hundred thousand dollar theatre, literally, as it were, in the dark, and partially ignorant of the condition of the projector until its condition becomes so bad that the effect is seen upon the screen and is heard in the sound," said Dr. Goldsmith at the meeting. "Then it is too late — the audience has seen the effect, consciously or uncon sciously, the audience carrie> away a feeling of dissatisfaction, the magnitude of which depends upon the seriousness of the circumstance, and may look elsewhere for better pictures and better sound. "When the projection practice committee will have completed its work of determining all the tolerances, clearances, and tensions for all moving parts of the projector, as it has set out to do, and of determining the amount of wear to which these parts may be subjected with safety, it will have completed an invaluable piece of work. "But the final economic results of the work will have been achieved when the committee successfully indicates the simple means to be used by the projectionist to check these things, and the design of a cheap and simple kit of tools which he may use to do so. The Society of Motion Picture Engineers should do its best to make it easy for the projectionist to determine the exact condition of the projectors and to prove the occasional and timely need for replacement parts to the properly economical exhibitor. This means money in the exhibitor's pocket through better audience reaction, and also a more satisfactory and dignified position for the projectionist. "Flicker, shaking of the picture on the screen, out-of-focus effects, poor sound reproduction, all of which can be caused by the wearing or the maladjustment of parts, will then be under the control of the projectionist, who will be able to check and to readjust or replace the faulty parts before they are allowed to annoy the audience, irritate the theatre owner, and drive away the patrons."