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.