Motion Picture Herald (Sep-Oct 1936)

MODERN PROJECTION PROJECTION * SOINI REPRODUCTION • ACOUSTICS Some Sound Problems of the Smaller Theatre • Discussing some of the more significant conditions especially confronting the small theatre operator who wants as good sound as he can afford By H. W. PARO SOUND REQUIREMENTS of the small theatre differ greatly from those of the theatre that counts its seats in the upper hundreds and thousands, and are more accurately met by modern apparatus than by any previous equipments, many of which originated as large-theatre systems pared down as far as possible. The peculiar and separate needs of the smaller theatre in apparatus as well as in cost are better met today than ever in the past. Portable tent and town hall motion picture shows also have their own specific requirements in sound apparatus, which are substantially, but not entirely, identical with those of the small theatre installation. Seven primary needs of the smaller house, with reference to sound, are observed here, each with respect to cost, size, emergency provisions, maintenance factors, simplicity, sound quality and acoustics. FACTOR OF COST While low purchase price is essential to the very small theatre, low installation expense is equally vital. The practical method of meeting this second requirement is to arrange to have all wiring and interconnections made, so far as possible, in the factory under conditions of mass production, and as little as possible by the local electrical contractor. There are advantages as well as drawbacks to the sound system composed of units made by a number of manufacturers, each unit serving a different function, but the utmost in economy is achieved by the apparatus in which all operations are combined, so far as possible, within the mechanism of a single cabinet. Where theatre connections remain to be made, as between amplifier and soundheads, and amplifier and screen speakers, special cables and connection blocks will simplify and facilitate even these small details of installation. PHYSICAL SIZE Small physical size, in spite of some drawbacks to be noted hereafter, is not only advantageous but often necessary. Small theatres do not commonly have large projection rooms, and in many cases projection room space is at a premium. Very often, also, space behind the screen is obtained only at the expense of revenue-producing seats, and small physical size is desirable in low speakers as well as in projection room apparatus. Small physical size, however, is only very slightly related to reduced sound power. With beam power tubes, for example, and 18-inch dynamic speakers of a modern design, small systems can now deliver all the volume needed for small theatres (perhaps enough for quite reasonably large ones). EMERGENCY PROVISIONS Small theatres are usually located at a distance from sources of spare parts and engineering service, and are also more likely, as a group, to be subjected to excessive fluctuation of power line voltage than the larger theatres are. In spite of the pressing need for low cost, equipment for the smaller theatre must first of all things be sturdy, capable of standing up under unfavorable conditions of line voltage. Pref erably, it should also be designed to use tubes and other replacement parts that are easily available. MAINTENANCE FACTORS Maintenance costs and difficulties are greatly reduced by the use of inexpensive component parts, less costly to replace than to patch and nurse along, by use of components readily available, and, again, by sturdiness of construction that in itself eliminates most maintenance questions. Another important maintenance aid is provision for easy testing and checking with common, inexpensive testing appurtenances. SIMPLICITY OF EQUIPMENT Original cost, installation cost and maintenance cost and trouble are all reduced by use of the simplest available procedures for producing the required results. Thus, for example, there are definite advantages in multiple speaker systems, in which different banks of speakers operating through filters reproduce different bands of sound frequencies. But the advantages of simplicity lie with the use of dynamic speakers, now readily purchased, that cover the entire band of frequencies photographed on the sound film. Again, better sound is possible with d.c. exciter lamp supply than can be obtained when the exciter lamps are powered with a.c, but the second method eliminates a complete rectifier and filter system, and still delivers sound quality that quite probably may be regarded as adequate under the circumstances. FACTORS OF COST In connection with sound quality, it should be remembered that the smaller, more intimate theatre possesses inherent advantages, for which the larger theatre compensates usually only at the cost and trouble of using highly refined apparatus. The smaller theatre, first of all, permits a greater sense of intimacy between the audience and the nearby screen. The average small theatre has acoustic advantages of no little importance. Sound distribution is usually easy to obtain, even with flat baffles, except possibly in the extreme front corners. Not only the main body of sound, but also the difficult high October 17, 1936 39