OPEN AIR THEATRE

CASE STUDY

(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.

PLAN

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.

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)

• 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

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

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).

(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

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

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

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

• 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