Theatre Design & Technology - Winter 1981 - 21

A Sound
Control
Board
for
the
Theatre
by Rollins Brook
Electronic sound reproduction is the newest major tool of the
theatre. It was not until the mid-1920's to early 1930's that
technology provided the possibility of using electronic sound in
the theatre, and only in the last twenty years has it become
possible to achieve a realistic sound quality and to achieve the
degree of reliability required of a tool in a live performance.
While microphones, loudspeakers, and tape recorders have
been well-developed, sound-control equipment specialized for
the needs of the theatre has been slow to appear. Within the last
few years considerable attention of users and manufacturers
has been focused on developing improved control facilities.
A theatrical sound system should be able to pick up a sound
anywhere (live microphone or tape), process it in any manner
(tone, time-delay, reverberation, gain, etc.), and reproduce it at
any volume level from any combination of loudspeakers located
anywhere in the theatre. Thus live sounds may be combined as
needed with recorded sounds and reproduced from any point or
moved about the theatre as the director wishes. The need for
reinforcement of live stage sound is highly variable. In some
small theatres there might be no need for a microphone; in a
large theatre, reinforcement of both speech and music could be
the major demand on the system. Frequently the system is also
called upon to provide outputs for recording, broadcasting, and
monitoring onstage and backstage.
One of the first considerations in the sound system design
must be the functions to be incorporated and whether all
functions are to be controlled from a single point or to be divided
among two or more control boards. A large, specialized music
hall (such as the Grand Old Opry) would be likely to have three
control systems: house reinforcement, onstage monitoring, and
broadcasting/recording. Many large church systems are subdivided into reinforcement and broadcasting/recording control
functions. Even in a moderate size theatre, the reinforcement
and effects activities, ideally, should be controlled by two
operators at two different positions. Reinforcement control
should be from a location within the audience area in order that

the operator may hear the sound as the audience does. Effects
control should be from a booth where noise of tape machines,
etc., would not be a distraction to the audience. In fact, however,
there are rarely architectural or technical provisions for in-thehouse reinforcement control, so a single operator at one desk is
the general rule. This article focuses on this all-purpose control
board.
The primary purpose of the control board is to select and
process sounds from microphones and recorded media and to
assign them to various loudspeakers. Microphones are easily
portable and can be located anywhere in the theatre. Loudspeakers, however, are large and heavy and are somewhat
limited in the number of practical operating locations. Built-in
loudspeaker systems are commonly provided in those locations
that will be used most. Receptacles for portable loudspeakers
are installed in all other locations (often twenty to forty circuits).
The permanent loudspeakers are usually one to three groups
above or around the proscenium. Some theatres also have
loudspeakers located in audience rear walls, side walls, and/or
ceilings for envelopment effects or assisted reverberation (ambiophony). In addition to the audience-oriented loudspeakers,
there is frequent need for loudspeakers onstage for monitor foldback to the performers.
It is most unlikely that all microphone and loudspeaker
positions would ever be used in one production. The control
system, therefore, needs active control of only a limited number
of each. Through the use of patch panels and switches, any
needed microphone and loudspeaker lines can be assigned for
use. (Figure 1 shows a simplified block diagram of a typical
theatrical sound system.) The number of input channels required on the control board depends upon the number of
recorded effects that overlap or that come in fast cues (six will
almost always be enough) and upon the quantity of reinforcement microphones required (from none to twenty-four or more
for a large musical). The number of output channels depends
upon the number of different output mixes required simultaneously. These would include one to three channels for reinforcement, two for control room monitoring, one or two for
recording and/or backstage monitoring, and four to eight for
effects and on-stage monitoring. Generally eight to sixteen
output channels are sufficient.
The reinforcement and monitoring functions depend heavily
on the mixing ability of the board, and in these uses it is quite like
a typical mix-down board. The effects functions, on the other
hand, are really much more a problem of distribution. It is in the
this area of distribution that the theatre board becomes a unique
device. Figure 2 is a one-line diagram of the main signal paths of
a typical theatre board. The signal enters through a pre-amp
where it is processed and switch-assigned to any combination of
pre-set buses. Each of these pre-set buses has a master gain
control which acts as an input control for a row of a matrix of
volume controls. Each column in the matrix is an output to a
loudspeaker (or recorder, broadcast line, etc). The matrix is the
heart of the distribution system and is the feature which distinguishes the theatre board from a recording board. Here various
input sources may be proportionately assigned to various combinations of outputs. These assignments may be set up in
advance of need (hence, pre-set) and brought into action by use
of the PRE-SET MASTERS. Thus one complex distribution
pattern may be easily changed into another pattern by the
movement of a couple of controls. This system also allows
special mixes to be created for broadcast, onstage monitoring,
etc.
A major design decision (and cost factor) is to what extent
should the theatre board have provisions for electronic memory
control. Memory-assist systems are becoming the rule in today's
theatrical lighting systems, and the complex mix-down process
in modern sound recording is often accomplished only with the
aid of computerized control. Sound control for the theatre is far
more complex than the unidimensional (intensity only) control of
lighting; and it must operate in real time, unlike the record mixdown which can be repeated until perfection is achieved. In live
theatre there must always remain an easy and direct access to

Table of Contents for the Digital Edition of Theatre Design & Technology - Winter 1981