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Uploaded on: November 21, 2025

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Photo courtesy of the Ross King photo collection…

Photo - This is an ornate plaster box that contained an AP speaker (know as an Audience participation speaker) this was used by Hoyts to present a 4th surround channel when screening CinemaScope movies (such as The Robe)-The speakers were placed along the sides and back of the theatre for atmospheric and ambient effects. The Rialto had a number of these placed around the theatre wall - reference the attached photo.

Full description - A surround channel for atmospheric and ambient effects, sent to speakers along the sides and back of the theatre

Magnetic Tracks: Early systems used four analog magnetic tracks on the edge of the film, which allowed for more channels than the standard two optical tracks. Four Channels: The four tracks were used for: Left channel speaker / Right channel speaker Center channel speaker for dialogue and on-screen sounds A surround channel for atmospheric and ambient effects, sent to speakers along the sides and back of the theatre.

Contributed by Greg Lynch -