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SOUND TRACK THEATRE BOOK
Acoustical installation along the rear wall of the Ambassador Theatre, Baltimore, Maryland
Where curved back walls are encountered, it is recommended that the curve be adjusted so that the center of the radius of the arc will fall well back of the speakers and the screen. A smaller curve is sure to focus annoying echoes somewhere in the audience area.
Area Beneath the Balcony
Areas underneath balconies are considered as separate rooms. In most instances only the back wall is treated, no treatment being given the underside of the balcony, which really constitutes the ceiling of this "room".
Ceilings
In theatres without balconies, or with small, flat balconies, ceilings are low enough that they furnish useful reflection of sound from the screen and thereby help to maintain more uniform loudness from front to back of the seating area. Low ceilings should therefore be left untreated. Where a non-acoustical fibre
board has been used for ceiling finish, it may be painted to increase its reflectivity.
Ceiling heights of more than about 2 5 feet in the front of the room tend to produce delayed reflections and reverberation, particularly of the bass tones from the comparatively non-directional low frequency speakers. High ceilings should consequently be acoustically treated, at least in the front portions.
Front Wall
A blanket of a material similar to Ozite carpet lining, the size of the screen opening and hung loosely against the wall, is effective in eliminating back-slap from a wall behind the horns. This treatment absorbs the "standing wave" that is sometimes set up between the horns and the wall, and also kills reflections from the rear wall to the front. Rock wool, supported by wire netting, has been used, but when this is employed, a dark covering should be placed in front of it to prevent light reflection from getting back into this