Theatre Design & Technology - Feb 1974 - 24

precise timing of curtain calls and entrances can be
accomplished by a skilled operator.

figures give an approximate indication of the necessary
outlay in each case to accommodate a full orchestra:

3. Shell rigging

Articu lating shell
1/2 - 3/4 Ibs per square foot

$15,000 - $ 25,000

Articulating shell
3/4 - 1 % Ibs per square foot

5>30,000 - $ 75,000

Contained end room shell

$50,000 - $200,000

Articulating shell
in contained stagehouse box

$75,000 - $300,000

(a) Contained end room shell
I n the theatre there is only one recommended method
of properly handling a contained shell.

In view of its large mass density, there has to be some
special electro-mechanical system developed to allow the
shell to be stored in various locations along stagehouse
walls and moved into position when used.
In the past, mechanised contained end room shells
often meant that the house carpenter had to give up quite
a few of his available line sets. Today, however, some very
ingenious solutions have been developed that allow him a
full complement of house rigging.
The rigging of a contained shell weighing 2 Ibslsquare
foot or more is a highly complex technical project and
should be the subject of a separate paper.
(b) Articulating shell

1

Reverberation time throughout the frequency spectrum and the
ratio of direct to reflected sound.

2See list of goals, P. 17.

APPENDIX I

Excerpt from:

Medium weight articulating shells may be moved on
casto red dollies that can be rolled into separate storage
areas when the stagehouse is used for purposes other than
concerts. (Obviously, storage space for the dollies must be
part of the total stage design.)
The ceiling units of a medium weight shell can be
flown vertically in the fly space if one is willing to give up
three or four line sets for storage purposes. When
necessary, the entire ceiling can be moved to an unused
line set in the event the carpenter needs to use a specific
line set on which shell ceiling units are normally stored.
The heavier 1-1% Ibslsquare foot units are often
handled with some electro-mechanical system.
Shells weighing v,-% Ibslsquare foot can be manually
erected from storage positions along the stagehouse walls.
The most compact of these designs would take up a space
no more than 4 feet x 3V, feet, 2 feet x 7 feet or 1 foot x
14 feet.
For maximum effect, the articulating shell must be
coupled to the stagehouse with a scrim curtain, and the
main act curtain must be raised above the level of the top
of the proscenium.
4. Costs
The cost of a shell depends on the nature and
sophistication of the installation as well as the design of
the auditorium's architecture. However, one could
generalize in terms of the relative cost of the various types
of shell design.
Full stage enclosures have been built for major
symphony orchestras at prices ranging from $15,000 to
$300,000, including the cost of rigging. The following

24

NOTES

~

Dr. T. J. Schultz, "Acoustics of the
Concert Hall",
I.E.E.E. Spectrum, June 1965

"The subjects' responses confirmed that it is difficult
to tell whether or not low frequency energy is present in
the direct sound. When all frequencies below 250 cis were
removed from the direct (and early) sound, the test
subjects sensed this as a significant decrease in bass only
39% of the time. Note that even in a test in which the
examples were presented in quick succession for easy
comparison, and in which the subjects were warned what
to expect, they failed to detect a lack of low frequency
energy in the early signal most of the time. Apparently it
is not important that early reflections have a full
complement of low frequency energy . ..
On the other hand, when the energy below 250 cis was
removed from the reverberant sound, the test subjects
regarded this as a significant decrease in bass 93% of the
time. The perception of warmth (or rich bass sound),
though apparently independent of a spectrum of the early
sound, is lost when the late-arriving reverberant sound is
deprived of its low frequency energy. The ear seems to
judge spectral balance in terms of an integration over
several hundred milliseconds. It is willing to wait for the
reverberant energy before making its evaluation of musical
warmth. Thus' the reverberant field can stabilize the
overall spectral balance despite low frequency deficiencies
in the early sound. Since the early sound does not appear
to require low frequency energy, the early reflections
needed for intimacy in a large hall can be returned from
relatively small surfaces. Large reflecting panels not only
do not add any significant quality to the early sound, but
there is a danger that they may upset the critical energy
balance by weakening the reverberant component."

THEATRE DESIGN AND TECHNOLOGY

FEBRUARY, 1974
Table of Contents for the Digital Edition of Theatre Design & Technology - Feb 1974
