Operating instructions

INTRODUCTION

WHY A CINEMA PROCESSOR?

Originally, stereo sound on motion picture film was possible only by means of

magnetic striping, which was introduced in the 1950s. Although capable of

very good sound, this was such a costly approach that by the 1970s relatively

few films were being released with stereo soundtracks.

Then in 1975 Dolby Laboratories introduced the stereo optical soundtrack

originally known as Dolby Stereo. It provided the multichannel sound associated

with magnetic soundtracks in a much more practical format.

Getting high-quality stereo sound from an optical soundtrack required the

application of several new processes. It was necessary, for example, to

electronically “fold” four sound channels into just two physical tracks on the

film, and then “unfold” (decode) them on playback in the theatre. Dolby noise

reduction, a form of signal processing that greatly expands the limited dynamic

range of optical soundtracks, was also used, and requires its own special

playback processing circuitry.

Thus the cinema processor was introduced as a new element in theatre sound

systems. In addition to properly decoding Dolby encoded soundtracks, Dolby

processors such as the CP45 also provide equalization circuits that optimize the

frequency range of the projector’s optical soundhead and the theatre

loudspeakers. The diagrams below show the role cinema processor plays in

bringing your audiences thrilling, multichannel Dolby sound.