Theatre Design & Technology - Fall 2012 - 56

The TiMax GUI for PC and
Mac provides a familiar
environment for programming
input, output, and matrix
levels and delays, as well as
parametric EQ, group faders,
snapshots, and show libraries.

to every loudspeaker for the sake of complete coverage, we
elected to take advantage of source-oriented reinforcement
techniques to ensure that the actors would be localized more or
less accurately and immediately.
Source-oriented reinforcement is based on the Haas (or
precedence) effect-the localization of a sound by a listener in
the direction from which it first arrives at the ears. By carefully
programming signal delays to each of the fourteen loudspeakers around the site and ensuring that the level of the reinforcing
audio was no more than 6-8 dB greater than the level at an actor's position, we were able to assist the audience in localizing
the actors, rather than the nearest loudspeaker. Because the
cast was not confined to a single performance stage, however,
this meant dynamically varying the levels and delays according
to the actors' movements throughout the park.
In addition to a programmable routing matrix, we clearly
needed some hefty digital signal processing (DSP) power, and
this is where the TiMax2 SoundHub stands alone. Like a Swiss
Army knife for audio, the SoundHub combines a number of extremely useful functions in a single package: a routing matrix
available in multiples of 16 inputs x 16 outputs up to 64 x 64,
with sufficient DSP to afford control of level and delay at each
of the 4,096 crosspoints, as well as four-band parametric EQ on
each input and eight-band parametric EQ plus delay on each
output. An integrated hard disk is also included for sound effects replay, the number of available tracks being equal to the
number of inputs. All of this is packaged in a 2-RU enclosure.
For our purposes, a 16 x 16 SoundHub with 16 tracks
of random access playback was adequate. We used ten inputs
for sound effects playback and reserved six for dialog groups.
Sutherland and I loaded the SoundHub's hard drive with the
individual, edited effects tracks that would make up the soundscape. Even though the SoundHub allows loops to play within
loops playing within loops almost ad infinitum, I elected to
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edit and produce the individual effects tracks in ProTools,
simply because of my familiarity with it, and then import the
finished tracks into the SoundHub for routing and playback,
programming loops as necessary.

Localizing Performers
For accurate localization, every audience member should receive an acoustic wave front from each performer about ten
to twenty milliseconds before receiving the reinforcing energy
from the loudspeakers. Within this short time difference, the
brain integrates the two arrivals together as one sound, but
causes the listener instinctively to localize to the slightly earlier
sound arriving directly from the performer.
TiMax2 achieves this by setting up multiple unique delay
relationships between the performers' wireless microphones
and each loudspeaker reinforcing them. These relationships
are changed every time a performer moves to a different location
in order to maintain the acoustic precedence that makes the audience localize to the performer and not to the loudspeakers.
The TiMax2 software simplifies the process by allowing
localization zones to be predefined as image definitions, which
are simply tables of level and delay instructions preprogrammed
into the SoundHub, instructing it to place the performer's audio
image in the appropriate zone.
"There's no black magic involved," said Dave Haydon, director of Out Board, the UK company that developed TiMax2.
"TiMax is based on psychoacoustics and the physics of sound,
primarily the Haas effect that allows us to localize a sound
source in space using interaural cues based on time difference
of arrival of a sound at each of our two ears."
After programming the image definitions with routing and
level for each of the soundscape tracks, we shipped the SoundHub to Chris Baron at Frischkorn Audio Visual so he could begin programming image definitions for the actors.
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