| Phased PointSource Technology
™ |
Proprietary Non
Proprietary Engineering Manufacturing |
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PPST
Phased PointSource Technology™ (PPST) was initially designed
to solve a major problem with large-scale sound reinforcement.
More transducers can generate the desired sound output but fewer
transducers create better sound. Introduced as a core technology
in the KF900 Series to specifically address this large-scale
complexity, PPST is an ultra-sophisticated process of measuring,
modeling, and optimizing arrays. PPST involves generating high-resolution
measurement data for each separate element of a loudspeaker
array and using this to model performance at a variety of listening
locations. For this purpose complex data, with both frequency
and phase information, is used. The goal is to manipulate the
signal path of each array element for maximum integration and
minimal interference. PPST is then capable of specifying DSP
configurations for each transducer/horn element. These DSP-controlled
elements are used to create arrays custom configured to venues
ranging from moderately sized music sheds to the largest stadiums.
In the case of larger venues, consistent SPL can be maintained
over the entire audience area - from just 25 feet below the
array to over 700 feet away from the system.
The PPST Process
The PPST meausrement/modeling/optimization process creates specific
DSP settings for each cell in the array. In the case of the
array illustrated above, 14 different DSP channels are required
to drive each column.
The process begins with a round of precision measurements of
each cell of the loudspeaker array in the exact position the
modules would occupy in an array. Measurements are accurate
to 1/10th of an inch or 10 kHz.
Using microphones set at fixed positions around our test facility,
phase and frequency measurements are taken on-axis as well as
at 15, 30, 45, and 60 degrees below the horizontal axis.
After the data are normalized to 1/6th octave resolution and
"windowed" to isolate first arrivals, the results of the entire
measurement round are fed into a proprietary goal seeking computer
program called F-Chart. F-Chart sums the measurements of each
cell to create a composite frequency response plot for the entire
array and then manipulates delay and amplitude parameters for
each cell to align response at each of the five measurement
angles.
EAW engineers monitor F-Chart's progress -- usually over the
course of a few days -- until they feel certain that total system
response has been optimized and then fine tune the DSP settings
for use in a specific venue. Using the venue's actual geometry
and intended array location, the vertical beam profile is custom
tailored.
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KF900 Series array shown with each module
in a different color. Complex pre-configured DSP integrates
the modules into a single acoustical entity. |
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These illustrations show predicted
average dB SPL at a variety of locations along the central axis
of the array (upper left) at Olympic Stadium. Each white arced
line represents a 6 dB difference ranging from 97 dB SPL (far
right) to 127 dB SPL in front of the array.
The black lines indicate the measurement angles of 0, 15, 30,
45 and 60 degrees below the horizontal axis. Distances were
calculated to provide accurate representation of high frequency
losses due to air absorption.
At both 500 Hz and 6.3 kHz, all listening positions receive
sound at a level somewhere between 96 and 105 dB or ±4.5
dB. On-site adjustment at installation brought actual response
to within ±2 dB.
PPST accepts the well-documented but poorly understood
effect known as air absorption as an important parameter to
address when designing long throw arrays. Using a technique
we call high frequency pre-emphasis PPST arrays project HF
information more than 700 feet. Even level and frequency response
at distant listening positions results from uneven response
at 1m. Note how much "hotter" it is right in front
of the array at 6.3 kHz as opposed to 500 Hz.
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To read more about PPST, please read
the PPSTwhitepaper
in .PDF format.
Products that utilize this technology:
KF900 Series
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© 2002, 2003 EAW Inc.
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Eastern Acoustic Works, 1 Main Street, Whitinsville MA 01588
Phone 508 234-6158 | Fax 508 234-8251 | E-mail info@eaw.com |
