Theatre Design & Technology - Feb 1966 - 20

Christopher Jaffe, Stagecraft Corporation

ABSTRACT: Successes in recent years with lightweight fibreglass concert shells seem to refute the
traditiona I bul k-den s ity theory. A practi tioner describes his application of "selective reflection".
I. R. CODE: (CONCERT HALLS / ACOUSTICS /
EQUIPMENT)

The subjective standards of musical sound have
gi ven ri se to a wi de range of empi ri cal theori es
which have confused rather than clarified issues.
However, since musical acoustics is still as much
an applied art as a science, we must continually
reevaluate theoretical concepts in light of new experience.

construction of enclosures which in most cases
are impractical and unsuitable to theatre practice.
Although experiments indicate the validity of the
bulk-denSity principle in the listening area of the
auditorium, there is no evidence to justify its
application to the design of the concert enclosure
itself.

As a consultant on musical acoustics with a background in theatre praduction, I fully reali ze the
importance of good acoustics in an auditorium. The
word "auditorium" itself is indicative of one of
the building's main functions. However, other elements of good theatre design should not be compromised in the interest of "better acoustics" without
careful consideration of what actually determines
better orchestral sound.

Several years ago, in conjunction with my work in
the design, installation and tuning of demountable
shells, I became convinced of the importance of
designing concert enclosures which could control
the sound energy output of the individual sections
of an orchestra using adjustable reflectors built of
lighter materials having a higher percentage of
reflection In the mid-and high-frequency range.

The design of a demountable concert shell involves
some of the most critical acoustical decisions that
an architect must make. It must effectively complement the architectural acoustics of the bui Iding
whi Ie blending and balancing the sound produced
in various types of performances without interfering
with the day-to-day operation of the theatre.
In the past, extremely heavy reflector panels were
thought to be necessary for good concert acoustics,
and some of the most powerful "battleships" in the
fleet can sti II be found on the stages of leading
auditoriums throughout the country. This "bulkdensity" or containment approach to concert shell
design has its origin in auditorium architectural
acoustics and emphasi zes the importance of equal
reflection of sound energy throughout the musical
frequency range from the walls and ceiling surfaces
of the listening area. When applied to the design of
a concert shell, the containment theory implies the

20

DESIGN PARAMETERS OF A CONCERT SHELL:
In order to understand better the theory of source
balance through selective reflection, one must go
back to the design objectives of a concert shell.
Basically they are as follows:
A. Balance the acoustical energy output of the
various sections of the orchestra to produce a rich,
full-bodied orchestral tone.
B. Counteract the directional characteri stics of
individual instruments and blend them into a single
musical entity.

C. Project and distribute the sound as effectively and efficiently as possible within the acoustical
limitations of the listening area.
D. Contain and preserve as much as possible
of the total sound energy generated by the orchestra.
E. Enable the musicians to hear themselves and
each other.

I OSITT

THEATRE DESIGN AND TECHNOUXlY



Table of Contents for the Digital Edition of Theatre Design & Technology - Feb 1966

Contents
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Theatre Design & Technology - Feb 1966 - 2
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Theatre Design & Technology - Feb 1966 - Contents
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