two case studies of open air theatres

1. OPEN AIR THEATRE
CASE STUDY

2. (1) HOLLYWOOD BOWL
 Location : Hollywood, California.
 Capacity : 18000
 The Hollywood Bowl is known for its band shell, a
distinctive set of concentric arches
 The shell is set against the backdrop of the Hollywood
Hills and the famous Hollywood Sign to the Northeast.
 The "bowl" refers to the shape of the concave hillside
the amphitheater is carved into.

3. PLAN

4. HISTORY
 1928, Lloyd Wright built a shell in the shape of
concentric 120-degree arches, with movable
panels inside that could be used to tune the
acoustics. It was designed to be easily
dismantled and stored between concert
seasons
 1929, the Allied Architects built the shell using
a transit skin over a metal frame.
 By the late 1970s, the Hollywood Bowl became
an acoustic liability because of continued
hardening of its transit skin.

5. ACOUSTIC SYSTEMS
 Sufficient emergence of directly propagated sound and its reinforcement through early positive sound reflections
(from the amphitheatre gradient and natural loudspeaker response of the space),
 Control of late sound reflections (limitations of the reverberation time, eliminations of echoes)

6. • The ring-shaped structure hung within
the shell, supporting lights and
acoustic clouds
• Grand acoustic canopy that floats as
an elliptical ring above stage and
reflects the sound waves to all parts of
the stage
• A series of computerized translucent
louvers extends across the ring which
programmed to shift into place
according to the music performed

7.  The stage canopy is composed of
aluminium and fibre glass ring spanned
by folding polycarbonate panels
 The panels lie 10 degree above
horizontal curved surface to disperse
sound from instruments below

9. SOUND SYSTEM
 The current sound reinforcement system is a line-array configuration of
multiple loudspeaker enclosures hung vertically in a curved manner, with the
lower enclosures facing the front sections, and the upper enclosures angled
towards the rear sections.
 It includes state-of-the-art audio processing allowing each individual
loudspeaker directed towards the near-precise location of the listener,
regardless of where in the venue they are sitting.This results in the audience
in the rear sections hearing the same audio, at the same level, as in the front
sections.
 This electronic processing includes sound level, frequency equalization,
occasional special effects, and time delay (sound passes through wire much
faster than through air, therefore the sound coming from the speakers must
be delayed, allowing the actual sound from the stage to "catch up" so both
sources reach the listeners' ears simultaneously).

10. (2) RED ROCKS AMPHITHEATRE
 CAPACITY:9500
 STRUCTURE: Open air amphi theatre with covered
stage
 Red Rocks Amphitheater is a natural, geologically-
formed, open-air amphitheater located in Morrison
 Red Rocks Amphitheater is the only naturally-
occurring acoustically perfect amphitheater in the
world
 Upper plaza of the amphitheater sits at 6,200 feet
above sea level and offers views over the top of
Stage Rock and down across the landscape into the
city of Denver

11. DESIGN
 Red Rocks was known for its strong
acoustics and nearly rectilinear
design
 The rectilinear layout is nestled
between three monolith stones
 The upper plaza capture the views
of Denver and provides refuge from
the concert as tree lined pathways
separate the performance space
from the circulation

12. SEATING
 Because of its steep slope, every seat at Red Rocks is a good seat.
 The seating area consists of 70-tiered rows with a capacity of 9,450.
 The seats are wooden planks with no backs that are fastened to a cement
foundation.
 The seats provide an optimal seating that the audience helps to create a ‘back
wall’ to the amphitheater
 The main attraction to Red Rocks is the gigantic 300-foot sandstone monoliths
flanking the stage on either side, creating not only a beautiful natural setting for a
performance, but offering the closest thing to acoustic perfection

13. ACOUSTIC ATTRIBUTES
 The main attraction to Red Rocks is the gigantic 300-foot sandstone monoliths flanking the
stage on either side, creating not only a beautiful natural setting for a performance, but
offering the closest thing to acoustic perfection
 Monolith stones provide edges on three sides of the stage
 Monoliths lining the venue provide a surface for reflections of sound to bounce off
The intricate and complex faces of the stones
create all sorts of possibilities for reflections of
sound. Reflections can go to the back of front of
the venue, but due to their unparalleled faces,
never directly back and forth between surfaces,
thus avoiding a detrimental ‘fluttering’ of sound
between the two stones

14. • Multi faced surfaces contribute to longer reverberation times
• 30% slope of amphitheatre is best for sound projection and acts as a back wall
 There are only a couple dozen trees within the venue, all about 20 feet in height.
These contribute to some attenuation of sound, but because of their small size
and low number, have a very minimal affect on the sound of the space itself