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發表於 2012-7-23 19:59
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THE RISE OF THE MOTION PICTURE SOUND BUSINESS
In the late twenties, the success of "The Jazz Singer" established sound as the new standard for the motion picture theater. Western Electric, the manufacturing arm of AT&T, was destined to rule that business for many years. The vast resources of Bell Laboratories had been brought to bear on problems of recording, reproducing, and allied arts, and as a result they were able to mount the required technology for manufacturing in fairly short order. Electrical Research Products Incorporated (ERPI) was set up as a distribution company by Western Electric as a means of servicing the motion picture industry.
The early Western Electric theater systems were of one-way design consisting of large re-entrant type exponential horns. The Western Electric 555 driver was used with these large assemblies. Frequency response was band limited, and the range covered was probably no more than 100 Hz to about 5,000 Hz. Later on, Western Electric added a high-frequency unit as well as an array of low-frequency woofers to augment these systems. They used Jensen 18" woofers in open-back enclosures to supplement low frequencies and a device known as the Bostwick tweeter to extend the upper range. These additions to the basic one-way system appeared in 1931.
The sound department at Metro-Goldwyn-Mayer Studios was not happy with the augmented Western Electric systems. Specifically, they objected to the twelve-foot path length in the mid-range and its concomitant time delay relative to the low-frequency and high-frequency sections. The RCA systems of the same era were not even as good as the three-way Western Electric systems; they used a single eight-inch cone transducer mounted on a straight horn.
In 1933, Douglas Shearer, head of the MGM sound department, got the idea of building his own system. He enlisted the aid of John Hilliard, a young electrical engineer, and Robert Stephens, a design draftsman, who later was to found the Stephens Trusonic Company. John F. Blackburn, a physics graduate of the California Institute of Technology, suggested to Hilliard that MGM enlist the aid of James B. Lansing to manufacture components for the MGM system. The so-called Shearer horn system was introduced in 1936 and won an award from the Academy of Motion Picture Arts and Sciences for technical excellence. It was a large two-way system that had much in common with an earlier system that had been designed for auditory perspective experiments at Bell Laboratories. The Shearer system used high-frequency multicellular horns driven by a driver with an annular slit phasing plug. The low-frequency section of this system consisted of a large W-horn with fifteen-inch woofers operating in an open back configuration. Both woofers and high-frequency drivers had three inch voice coils. Flat wire was used in the high-frequency driver and round wire in the woofer voice coils.
There is no question that the Shearer MGM system set new standards for sound in the motion picture theater. The basic design was later adopted by many manufacturers around the world; both RCA and Western Electric adopted the basic approach for their later systems.
Western Electric objected to the use of annular slits in the high-frequency phasing plug the Lansing company had designed. Western Electric had patented this design, and as a way around this problem John Blackburn and Lansing devised a radial slit phasing plug, which they incorporated in the 284 driver. Later, Blackburn found a way around the Western Electric annular slit patent by noting in the literature that Bell and Tainter, in the early years of the century, had established prior art in the area of acoustical phonograph design.
Another important system that Lansing designed for the industry was the Iconic, a small two-way system using a fifteen-inch low-frequency loudspeaker and a small high-frequency driver, the 801 (later known in its Alnico form as the Altec 802), driving a small multicellular horn. The Iconic system gained wide popularity throughout the motion picture industry as a monitor loudspeaker; many two-way monitor systems of today are only minor improvements over this early system.
The United States government, taking note that Western Electric held a virtual monopoly in motion picture sound recording, forced that company to divest itself of all holdings in the sound recording business. Western Electric signed a consent decree in 1938 and sold the holdings of Electrical Research Products, Incorporated, to a group of engineers who were working for them at the time. The name, Altec, was coined for this occasion: Altec, a contraction of All Technical. The principals of this new company were George Carrington and E. L. Conrow. Their new company was called Altec Service Corporation and maintained contracts with theater chains around the country for system maintenance work. The Altec Service Corporation went about its business for two years without a source of new stock or parts. They used existing stocks of ERPI products where required, but their main business was service.
It became apparent to Carrington and Conrow that they would have to develop a source for new manufactured items if they were to be a viable force in the business on a long-term basis. In 1939, Ken Decker, Lansing's business partner and a reserve officer with the United States Army Air Force, was killed on maneuvers when the airplane he was piloting crashed. Without Decker, Lansing's business suffered, and it became apparent in 1941 that the sale of the company was the only way to keep it afloat. On 4 December 1941, the Altec Service Corporation bought the Lansing Manufacturing Company. They were reputed to have paid a price of $50,000 for the acquisition, and there were nineteen employees at the Lansing Manufacturing Company at that time. Lansing assumed the title of Vice-President of Engineering in the new Altec Lansing Corporation. Western Electric agreed to license the Altec Lansing Corporation to manufacture any and all of the proprietary designs that were covered by the consent decree. Royalties were never charged by Western Electric for items manufactured. |
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