Projection engineering (Jan-Dec 1931)

Page 22 PROJECTION ENGINEERING Class Theatres ACCORDING to the Cinematograph Times, London, in the July issue of The Builder, L E. G. Warland, A.I., Struct.E., writes interestingly upon "The Walls of Tomorrow," and deals with the possibilities of glass and other translucent material. He visualizes, and illustrates his article with a drawing of the supertheatre of 1933, the main elevation of which is worked out in broad bands of glass, illuminated from behind and providing a very striking background for publicity material. "I visualize," he says, "before long for certain classes of buildings that we shall have a lighter steel-skeleton framing. To this will be fixed sheets of glass, or other thin material, for the external face, and on the inside will be fixed sheets of reinforced plaster, cork slabs, asbestos-cement sheets, or clay blocks. The void between these two skins, which will form permanent shuttering, can then be filled with concrete. ... I think of the possibilities of this new method; imagine a glass-fronted theatre, faced in, say, blue and orange glass and lighted up in bands of color and light from behind. Obviously there is scope here for original and striking design — a cheap, effective and easily cleaned facade. I can only hope that those who step in and take advantage of this opportunity will prove themselves worthy of it, and not produce something merely novel and gimcrack." That so far-seeing an engineer as Mr. Warland should visualize the coming of a new and attractive type of picture is likely to meet with greater interest at this juncture, when variation of the usual types seems to have reached something approximately the margin of limit. Two well-known and experienced technical men, John Wilson, chief engineer of the Gramo-Radio Company, Accrington ; makers of the typical theatre horns and loudspeakers, and C. Hartley Davies, S.M.P.E., B.K.S., seem, however, to have previsualized the possibilities of cavity wall construction internally illuminated last year. They put their idea to the practical test of application for patents in their joint names. This invention related to illuminated walls by cavity lighting and heating, and has for its object the reduction of the gross weight of high buildings, and the lowering of building costs, while providing permanent and ornamental decoration. It consists essentially of a building, the skeleton of which is of steel and the outer shell of known building materials. The inner walls of such building, however, are not made from the known building materials ordinarily used for the construction and decoration of interiors, but from marble, glass, or any other transparent or translucent material, leaving a cavity behind the facing material and between the steel stanchions forming the upright supports of the building for electric lighting and heating. By the use of mirrors and prisms in the cavities various lighting effects are obtained. Where desirable, not only the inner, but also the outer walls, are made from the transparent or translucent materials already mentioned in preference to the known building materials, and such exterior walls are also provided with cavities behind for electric lighting and heating. Where exterior walls are constructed in this manner, and in particular frontages, brilliant effects are obtained at night. DE FOREST PLANS TO REPLACE 1,000 DEVICES IN 6 MONTHS UNDER its new replacement plan, General Talking Pictures expects to make approximately 1,000 installations of De Forest equipment during the next six months. Theatres having De Forest devices are being offered replacement of more up-to-date equipment under a rebate arrangement. Forty of these replacements have been effected since the new plan was placed in operation, it is stated. ADJUSTMENTS FOR LIGHT VALVE RECORDING (Concluded from page 10) in correlation with the filament current producing this effect. This value will then be employed for all recording work with this particular lamp. A rougher method is possible if another lamp previously calibrated is on hand. Suppose for instance we have a recorder lamp known to give correct exposure when the filament current is 15 amperes. With this lamp in position an oscillator is patched to the light valve and the photoelectric cell internal to the recording machine is coupled through the amplifiers to an indicator. The oscillator having been set to, say, 1,000 cycles, attenuators are adjusted so that a mid reading appears on the meter. The recording lamp is then removed and the new and untried unit slipped in its place. The filament current is then adjusted so that it gives the same reading. It is better to check several frequencies, as in practice it is sometimes found that recording lamps do not always follow a straight line curve as regards actinic effect at different frequencies. MADISON SQUARE GARDEN TAKES THE SOUND CURE (Concluded from page 14) engineers of Acoustic Consulting Service of the Electrical Research Products Co. The result is a new ceiling considerably lower than the old one and still high enough to allow the circus trapeze artist all the movement she needs or to permit a gridiron star to punt his highest if night football ever becomes an innovation at the Garden, and the acoustic improvement has borne out the accuracy of the findings. It was estimated in the preliminary survey that as a result of such treatment the reverberation time would be reduced to a value of from 3.5 seconds when the hall was empty to 1.56 seconds with an audience of 18,000. Tests made under the new conditions proved these figures to be correct. SOUND PROJECTION PRACTICE (Continued from page 17) box-office returns that the expense of the change has been thoroughly justified. It is believed and hoped that more theatres can avail themselves of this improved condition not only for their own salvation but to give to the public all the benefits of the improved products which could not otherwise be realized. There has probably been a healthy although unconscious competition between the studio and the theatre in striving toward higher quality. Such improvements as better reproducers for disc records, finer optical systems, and smoother mechanical features for film reproduction, along with other general advances applicable to both methods, have raised the standards of the theatre equipment to the point where they are capable of handling good quality recordings. Improved technic in the studios, resulting from such factors as study of stage and set acoustics, microphone placement, better knowledge of re-recording methods, and more exact control of film processing, have made it possible for the studios to show a tremendous improvement in the quality of the recorded product. The gradual extension of the frequency range has been a material contribution to this improved quality but efforts toward a greater range should be and are being continued. (To be concluded)