Theatre Design & Technology - Oct 1965 - 15

effects and the movement s wh ich pan potent i ometers
supply, would require the pairing (at least) of

5. Beat Frequency asci Ilator (Genera I Radio
Model 1304B).
6. Sound Level Calibrator

speakers, each with its isolated circuit. Such elab-

(General

Radio

1552B).

oration cannot be achieved merely by adding program

7. Impedance

channe I s or two-channe I pan potent i ometers. In the

Bridge

(General

Radio Model

1650A).

sound system of the New York State Theatre, Lincoln
Center, a partial solution to this switching problem
has been achieved by means of a flexible matrix of

8. Distortion

interconnections

9. asci IIascope (Tektronix Model 593B with
Model (,12 Camera).

speakers.

This

between
is

not

program

unlike

channels

and

interconnection

of

10. Line

stagelighting load-and-line circuits. In that particular
installation

any

combination

of

speakers

can

Analyzer

(Hewlett

Packard

Model 330B).

Voltage

Regulator

(General

Radio

Model W5MT3AW "Variac").

be

switched to or from any of ten program channels, and
the state of the switching can be quickly ascertained,
from moment to moment, by visual inspection. 6
Rather than a need for more program channels, experience with the system described here has uncovered a different need in several cases where complex
effects were desirable in the use of sound around or
alongside
fects, or

Fami liarity
measuring

with the

nature

of

these

prafessiona I

instruments and high standards in oper-

ating procedure together constitute a cr;terion that
permits duplication of any test at a later date for
comparative

purposes

of

simi larities

and

differ-

the audience. Music, environmental efmoving sound effects were frequently

ences,

desirable on the same s ide of the audience at
the same time.
However, unti I circuit designs

charts

can

a

note on the difference between machine-run graphs

variable number of program channels to be fed into

and those plotted from individual measurements is

be

economically

developed

which

allow

a single power amplifier-speaker circuit at the same
time that it and some others are grouped on another
program channel without circuit feedback, overload,
attenuation, or distortion -- unti I such an ideal convenience is avai lab Ie, any such overlap of effects
would be expensive. Presently, it would require a

a

necessary

basis

to

insure quality com-

panents and promote reliable operation. Since many
are made in a series of tests like these, a

in order. The pen and chart speeds are shown on each
machine-run curve (Figures 4 and 5). The record of
the ratio of these two speeds is a very

revea ling

consideration since a change in these speeds alone
can

convert a

quality

of a

curve ex pos ing the

unit to

one touting

re lat ive Iy poor
its alleged, but

second set of power amplifiers and speakers paral-

illusory, professional quality.lfa frequency response

leling the present installation.

curve

were to be made at a pen speed of one inch

Testing

per second and the chart speed run at 75 inches per
minute, we could not expect to produce a curve that

While it is beyond the scope of this description to

contained much information. This setting would mean

cover testing procedures for such a system, the
"professional" standard of such a system is not es-

chart

tablished without such tests. For that reason neces-

sufficient time to allow the slow movement of the

sary testing equipment will be listed, important pro-

pen to deve lop a true pi cture of the peaks and dips
in a frequency response curve. To reveal the actual
variations
being
measured,
frequency response

cedures will be outlined, and sample results will be
provided.

Since the

particular models and manu-

that for everyone inch of rise or fall of the pen, the

facturer types specified for the components in this

curves

system were provided asasked,no "approved equal"

inches

would also move a

little over an inch: not

should be run at a pen

speed of 10 or 20

per second and the chart at a speed of 26

examination of performance quality had to be made. 8

inches per minute. Such ratios allow relatively accu-

Another specification, however, called for performance tests of the entire "effects" system in the

rate tracking.

University
response,
distortion,
level

TheCJtre:
equivalent

overall
input

reverberation

system

noise,

time,

and

frequency

overall
ambient

system
noise

The curves of Fig.
run, revea I the flat
amplifiers, program
at full rated output.

5, also the result of a machine
frequency response of the prechannels, and power amplifiers
Also listed for each situation is

tests were made. These were conducted by

the amount of equivalent input noise, a factor of the

Carl Colip, president of Commercial Electronics,
Inc., with the following instrumentation:

preamplifier stage, estimated in response to a 1,000
cycle signal fed into the preamplifier at -70 dbm.

1.

Sound Leve I Meter (Genera I Rad io Mode I
1551B).

2. Wave
Anolyzer
1554A).

(Generol

Radio

Model

3. Graphic Level Recorder (General Radio
1521A, with both 40 and 80 db. potentiometers ).
4. Random Noise Generator (General Radio
Model 1390B).

14

with a resultant
amplifier. Thi s
degree of noise
feren ce with the

output of -46 dbm. from the power
figure provides on estimate of the
inherent in the system and in interin format ion-carry ing potent ia I cf the

carrier wove in the system as well as a measure of
the gain. One of the weakest signals usually fed into
an effects system in the theatre, that of the microphone, is still safely stronger, if the specification
is met, than the equivalent input noise. As a result
there exists a favorable signal-to-noise ratio.

IUSITT

THEATRE DESIGN AND lECHNOlllGY



Table of Contents for the Digital Edition of Theatre Design & Technology - Oct 1965

Contents
Theatre Design & Technology - Oct 1965 - 1
Theatre Design & Technology - Oct 1965 - 2
Theatre Design & Technology - Oct 1965 - 3
Theatre Design & Technology - Oct 1965 - Contents
Theatre Design & Technology - Oct 1965 - 5
Theatre Design & Technology - Oct 1965 - 6
Theatre Design & Technology - Oct 1965 - 7
Theatre Design & Technology - Oct 1965 - 8
Theatre Design & Technology - Oct 1965 - 9
Theatre Design & Technology - Oct 1965 - 10
Theatre Design & Technology - Oct 1965 - 11
Theatre Design & Technology - Oct 1965 - 12
Theatre Design & Technology - Oct 1965 - 13
Theatre Design & Technology - Oct 1965 - 14
Theatre Design & Technology - Oct 1965 - 15
Theatre Design & Technology - Oct 1965 - 16
Theatre Design & Technology - Oct 1965 - 17
Theatre Design & Technology - Oct 1965 - 18
Theatre Design & Technology - Oct 1965 - 19
Theatre Design & Technology - Oct 1965 - 20
Theatre Design & Technology - Oct 1965 - 21
Theatre Design & Technology - Oct 1965 - 22
Theatre Design & Technology - Oct 1965 - 23
Theatre Design & Technology - Oct 1965 - 24
Theatre Design & Technology - Oct 1965 - 25
Theatre Design & Technology - Oct 1965 - 26
Theatre Design & Technology - Oct 1965 - 27
Theatre Design & Technology - Oct 1965 - 28
Theatre Design & Technology - Oct 1965 - 29
Theatre Design & Technology - Oct 1965 - 30
Theatre Design & Technology - Oct 1965 - 31
Theatre Design & Technology - Oct 1965 - 32
Theatre Design & Technology - Oct 1965 - 33
Theatre Design & Technology - Oct 1965 - 34
Theatre Design & Technology - Oct 1965 - 35
Theatre Design & Technology - Oct 1965 - 36
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http://www.nxtbook.com/nxtbooks/hickmanbrady/tdt_1968Dec
http://www.nxtbook.com/nxtbooks/hickmanbrady/tdt_1968Oct
http://www.nxtbook.com/nxtbooks/hickmanbrady/tdt_1968May
http://www.nxtbook.com/nxtbooks/hickmanbrady/tdt_1968Feb
http://www.nxtbook.com/nxtbooks/hickmanbrady/tdt_1967Dec
http://www.nxtbook.com/nxtbooks/hickmanbrady/tdt_1967Oct
http://www.nxtbook.com/nxtbooks/hickmanbrady/tdt_1967May
http://www.nxtbook.com/nxtbooks/hickmanbrady/tdt_1967Feb
http://www.nxtbook.com/nxtbooks/hickmanbrady/tdt_1966Dec
http://www.nxtbook.com/nxtbooks/hickmanbrady/tdt_1966Oct
http://www.nxtbook.com/nxtbooks/hickmanbrady/tdt_1966May
http://www.nxtbook.com/nxtbooks/hickmanbrady/tdt_1966Feb
http://www.nxtbook.com/nxtbooks/hickmanbrady/tdt_1965Dec
http://www.nxtbook.com/nxtbooks/hickmanbrady/tdt_1965Oct
http://www.nxtbook.com/nxtbooks/hickmanbrady/tdt_1965May
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