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BOSTON AUDIO SOCIETY
January 2010 Meeting
Date: Thursday,
January 14, 2010
CORRECTED TIME: REFRESHMENTS 7PM, MEETING 7:30
PM
Place: The Walsh Function Room @ Boston College
Featured Guest: Don Keele
Topic: The Boston Audio Society, Boston Sections of the Audio Engineering
Society,
and the Acoustic Society of America Presents: Introduction to CBT
Loudspeaker Arrays
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DON
KEELE |
Don Keele will talk about his line arrays based
on CBT technology. He has been an ardent advocate and evangelist for
the concepts for over ten years and believes the CBT knowhow can vastly
improve the sound field uniformity of existing line arrays and conventional
loudspeaker systems. Don will discuss the background and history of
CBT arrays and will describe and discuss the measurement and simulation
results of several CBT line array prototypes that were constructed
for home applications.
CBT, which stands for "Constant Beamwidth
Transducer', is a term originated by the U.S. military in a series
of three un-classified Naval Research Lab ASA papers published in
the late 70s and early 80s. These papers describe spherical-cap underwater
transducers with special frequency-independent "Legendre"
shading that provide extremely-uniform broadband coverage without
the need for any special or complex signal processing.
The CBT loudspeaker arrays provide directional
performance and sound-field coverage that borders on revolutionary.
The CBT arrays provide a broadband 3D sound field that is incredibly
uniform and well behaved with frequency at all distances from very
close to far away. The vertical bandwidth control and coverage of
the CBT line arrays often exceeds the finest constant-directivity
pro horns.
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| DEMONSTRATING
THE CBT LINE ARRAY |
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The CBT line arrays provide a very-tight extremely
well-controlled vertical sound-field coupled with a well-controlled
very-broad horizontal coverage. CBT array possibilities extend over
the full loudspeaker product range from professional, commercial,
consumer, home theater, computer, and multimedia
For the first time, these arrays provide the capability
to implement a true broad-band constant-bandwidth/directivity/coverage
systems in a home or pro environment. The so-called "ground-plane"
CBT arrays are specifically designed to operate near a reflective
surface such as the floor or ceiling, and to not suffer from destructive
floor-bounce reflections.
Don Keele has worked for several companies in
the area of loudspeaker R&D and measurement technology including
Electro-Voice, Klipsch, JBL, Crown, and Harman. He holds three patents
on "constant-directivity" loudspeaker horns, has four patents
pending, and is a fellow of AES and a member of ASA.
Mr. Keele received the TEF Richard C. Heyser Award
in 2001. In 2002, he received a Scientific and Engineering Academy
Award from the Academy of Motion Picture Arts and Sciences for work
he did on cinema constant-directivity loudspeakers.
Guests are always welcome at BAS meetings.
* Note that the event is on
a Thursday*
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