Theatre Design & Technology - Feb 1974 - 18

distribution, etc., are achieved by the floor, wall and
ceiling envelope of the hall in the vicinity of the stage,
producing results matching required acoustic criteria
(Appendix II, Fig. 1).
However, in certain single-space concert halls where the
envelope of the room in the vicinity of the stage does not
properly match acoustic criteria in relation to source area
design goals, suspended reflectors, articu lators, diffusers,
blenders and balancers have been added to ach ieve the
desired resu It. These suspended reflectors can change the

of the shell, and the other is to utilize an inner system to
meet certain criteria and the stagehouse or the walls and
ceilings of the stage side of the pavilion to meet the
remainder.
There are other possibilities, such as combining the two
design approaches by cutting off a portion of the
stagehouse to increase the sound pressure level of the

ratio of direct to reflected sound through portions of the

reverberant field

frequency spectrum, reduce the arriva I time of early
reflections in the mid and high frequencies, and enable the
musicians to hear themselves and other sections of the
orchestra more clearly. The Symphony Halls in

forward of the proscenium, utilizing a series of convertible

Stockholm, Berlin, Munich, Rotterdam, and now Sydney,
Australia, have incorporated these design techniques to
achieve improved sound quality (Appendix II, Fig. 2).
By definition, these reflectors or articulators suspended
within the volume of a one-room hall ca~ be categorized
as a form of acoustical shell or concert enclosure
constructed in the source area. Observation of these
examples of the shell design approach indicate that it is
not always essential to utilize the boundary surfaces of a
room to meet every source area criterion.

or by bringing the entire orchestra

forestage seating lifts and the fire curtain to create a
one-room space.
Based on recent experience, the cost of combin ing the
two design approaches is not warranted in terms of
contemporary presentation houses, where the stagehouses
are usually sold open and clear to the touring groups and
there are no repertory theatre or ballet companies
permitted to store scenery in the fly areas.
If one decides to bring the orchestra forward of the
proscenium, a decision must be made as to whether
criteria development takes the direction of the 100%
envelope approach or whether articu lati ng reflectors are
added as part of the design.

For example, if one attempts to reduce the amount of
high and mid frequency sound reaching the upper
reverberant portion of a room in order to enhance the
bass frequencies in the reverberant field, the suspension of
overhead panels and reflectors with dimensions that do
not exceed eight to ten feet will direct a high percentage
of the mid and high frequencies directly into the
sound-absorbing audience area. Low frequencies will, of
course, pass through the reflector grid to enter the
reverberant field
and return familiar bass-rich
time-delayed reflections to the listener. Such a panel
system will enhance the center orchestra section of any
concert hall in the world, since the receipt of mid and
high frequency information shortly after the direct sound
from the orchestra reaches the ear has the added
advantage of providing intimacy and definition.
In transferring the problems of developing acoustic
criteria from the one-room European rectangular hall to
either the American mUlti-purpose concert haliitheatre
with full stagehouse or the American fan-shaped
amphitheatre music pavailion, designers have the option
of selecting two different approaches to designing that
portion of the room designated as the source area (i.e. the
stage side of the European hall). Since both the
mUlti-purpose concert hailitheatre and many music
pavilions utilize their stage area for events other than
symphonic presentations, the walls and ceilings of the
source area directly surrounding the orchestra must be
readily demountable and usually are described as an
acoustical symphonic shell or concert enclosure.

18

One approach is to emulate the design direction of the
one-room space and attempt to meet all acoustical criteria
by use of the boundary surfaces of the walls and ceilings

~

Until the late 1950's most orchestras in multi-purpose
concert hall/theatres utilized reflector panels to develop
acoustical criteria in a rather crude and unsophisticated
way. Since more houses of the period were rigged with
hemp or counterweighted hand rigging systems, it was
impossible to consider meeting the proper criteria for a
contained shell, since the rigging systems could not move
the massive ceiling and walls required. Lightweight canvas
and plywood shells were quite popular as a means of
providing mid and high frequency reflected information
into the listening area, helping the musicians hear
themselves, and balancing and blending orchestral
sections.
In some instances, Carnegie Hall for example, when
these lightweight reflectors were utilized in such a manner
as to couple the volume of the fly space with that of the
hall, the resu Its were extremely gratifying and even
somewhat mystifiying, in view of the limited
psycho-acoustic information available at that time.
When electro-mechanical theatre rigging became more
soph isticated and it was possible to consider the
development of a contained shell utilizing the envelope of
the enclosure surfaces to meet all course criteria, several
practioners developed designs along these lines. The
advantages of the contained shell are: (a) a slightly higher
dynamic range can be achieved in the direct sound field;
and (b) one does not have to be concerned if repertory
opera, theatre or ballet companies {or a show whose run is

THEATRE DESIGN AND TECHNOLOGY

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