Theatre Design & Technology - Feb 1972 - 18

Careful overall equalization is as essential to a
surround and reverberation system as to a reinforcement system.

ity requirements for use of the stage house rule
out permanent overhead loudspeakers in most
theatres.

Control

* ACOUSTICAL ENVELOPE OR
STAGE COMMUNICATION
SYSTEM
Purpose
The acoustical envelope or stage communication
system may be provided to (1) allow singers on
the stage to hear the pit orchestra, if this has not
been accomplished by room-acoustics design; (2)
to allow performers on the stage to hear themselves better, with the psychological advantage of
believing that they're heard in the hall; (3) to allow
performers to hear each other better (an electronic
substitute, in part, for a missing concert stage enclosure); and (4) to provide on-stage coverage for
lectures, speeches, and conventions, where a significant number of people are seated on the stage.

Techniques
The techniques for providing on-stage sound
vary widely according to the application. The basic
problem, as with reinforcement systems, is providing enough sound for people to hear without
creating a feedback problem.

PORTABLE ON-STAGE LOUDSPEAKERS
At Milwaukee's Uihlein Hall and Houston's
Jones Hall, the sound-effects amplification channels are frequently borrowed for on-stage coverage
for speeches and for "fold back" for popular entertainers. The loudspeakers employed are those portables normally used for sound effects; they are
usually located at each side of popular entertainers
while covering the entertainers themselves, or located behind a lecturer while covering listeners
seated behind the lecturer. A variation on this technique involves wiring the loudspeakers in opposite
phase, while placing the loudspeakers so that the
resulting null zone includes the microphone pickup locations. Care is required to insure that listeners to be covered are not also in a null zone,
however.
FLOWN LOUDSPEAKERS
At Boston's War Memorial Auditorium linesource, or column, loudspeakers have been flown
horizontally, parallel to the longitudinal axis of the
auditorium, to provide coverage for listeners upstage, while restricting coverage (through the directional characteristics of the line-source loudspeaker) away from microphone positions. Similar
systems have been built into auditoriums that have
permanent stage enclosures or shells, but flexibil-

18

Proper control of an acoustic envelope system
invariably requires some trial and error during rehearsal time prior to the performance, since the
operator cannot actually control on-stage sound
from a position where he can hear it--on the
stage. Experience with a large number of events
in a particular facility can, of course, permit some
presetting for those events that move in without
rehearsal time.

* LOBBY LATECOMER SYSTEMS
Purpose
The main purpose of lobby latecomer systems is
to hold the attention of the latecomer, permitting
him to follow the performance, without actually entering the theatre and disturbing those who arrived on time. The same system may also serve as
the audience recall system, if extensive enough,
and may be used to provide intermission entertainment or background music.

Extent of System
The lobby latecomer system may employ one or
two loudspeakers covering one or two areas where
latecomers may be asked to wait, or it can be a
complete distributed loudspeaker system covering
all lobby and other circulation areas. A complete
system will be necessary if it is to be used for
audience recall. The lobby system may actually be
part of the overall monitoring system, and will certainly share the same microphones and perhaps the
same mixer-preamplifiers, but best result will be
obtained if the amplification channels are separate,
permitting equalization matching the lobby's acoustical characteristics and the loudspeakers employed.
CLOSED-CI RCU IT TV
Audio monitoring for latecomers may be supplemented by video monitoring, again with the main
purpose of encouraging latecomers not to interrupt
or disturb those already seated. The closed-circuit
TV system may be relatively simple, with a camera
in the balcony rail and monitors, coordinated with
loudspeakers, at the lobby walls. The camera
chosen must meet the illuminance requirements
imposed by normal stage lighting.

Possible Acoustical Interference
The lobby monitoring system, indeed all sound
monitoring systems, must be carefully studied to
insure that they don't affect the audience hearing
live sound and reinforced sound in the theatre

O§:] THEATER DESIGN AND TECHNOLOGY

FEBRUARY, 1972
Table of Contents for the Digital Edition of Theatre Design & Technology - Feb 1972
