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MEETING NOTICE:
The
next meeting of the Chicago Section of the Audio Engineering
Society is Tuesday,
April 23, 2013 . Meetings
are FREE. Members and non-members are welcome.
Not a member of
the AES? For information about joining, go to
http://www.aes.org/info/join.cfm.
PRESENTER:
Don
Keele of Audio
Artistry
DATE:
Tuesday,
April 23rd
TIME:
7:30pm;
dinner (optional) at 6:30pm
TOPIC:
Introduction
to CBT Loudspeaker Arrays
LOCATION:
Shure
Incorporated
5800
W. Touhy Ave, Niles, IL 60714 - Directions
below
ABOUT
THE PRESENTATION:
Come
out and hear Don Keele talk about his loudspeaker 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 know-how 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 arrays including the Audio Artistry CBT36
high-end home loudspeaker which is sold in an inexpensive DIY kit
form by Parts Express and finished form by Audio Artistry. The
CBT36 system will be setup for listening.
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. Don applied the
technology to loudspeaker arrays in a series of six AES papers
between 2000 and 2010 and some of the technology is now in the
public domain. The CBT arrays provide a broadband
constant-directivity 3D sound field that is incredibly uniform and
well behaved with frequency at all distances from very close to
far away. The vertical beamwidth control and coverage of the CBT
line arrays often exceeds even the finest constant-directivity pro
horns.
The
CBT line-array concept dictates that multiple loudspeakers be
placed evenly around a circular arc and that frequency-independent
shading (simple changes in level) be applied to each speaker. An
alternate, but much more complex, CBT implementation method is
based on the use of delays to provide the circular curvature of a
straight-line array. Circular-arc CBT arrays can be implemented
passively and do not require any sophisticated DSP signal
processing except for simple level changes. CBT array
possibilities extend over the full loudspeaker product range from
professional, commercial, consumer, home theater, computer, and
multimedia. Note that Harman/JBL has copyrighted the term “CBT”
in the loudspeaker industry where it stands for “Constant
Beamwidth Technology” and has three patents issued to Keele on
some of the CBT concepts.
ABOUT
THIS MONTH’S SPEAKER:
D.B.
(Don) Keele, Jr. has worked for several companies in the area of
loudspeaker R&D and measurement technology including
Electro-Voice, Klipsch, JBL, Crown, and Harman International. He
holds eight patents with topics including "constant-directivity"
loudspeaker horns, loudspeaker arrays, and signal processing. He
is a fellow of AES. For ten years he wrote for Audio Magazine as a
Senior Editor performing loudspeaker reviews. More recently, he
worked for Harman/Becker Automotive Systems in the advanced
technology development group and was a member of the Harman
corporate acoustics engineering group working under Floyd Toole.
Currently he heads his own consulting company DBK Associates and
Labs and recently joined loudspeaker manufacturer Audio Artistry
as VP of R&D. His passion for the last eleven years has been
to promote the use of CBT (Constant Beamwidth Transducer)
loudspeaker technology in the loudspeaker industry.
Mr.
Keele holds two BS degrees in EE and Physics from California State
Polytechnic University and an MSEE degree from Brigham Young
University where he minored in acoustics. He has presented and
published over 40 technical papers on loudspeaker design and
measurement methods and other related topics, among them the paper
for which he won the AES Publication Award, "Low-Frequency
Loudspeaker Assessment by Nearfield Sound-Pressure Measurement".
He is a frequent speaker at AES section meetings and workshops,
has chaired several AES technical paper sessions, and is a past
member of the AES review board. Mr. Keele is a past member of the
AES Board of Governors and is past Vice President, Central Region
USA/Canada of the AES. 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. In 2011 he received the ALMA Beryllium Lifetime
Achievement Award for contributions to the loudspeaker industry.
DIRECTIONS:
When arriving by car, approach from
the east by heading west on Touhy, then turn right into the
parking lot just east of the Shure building, which is on the
corner of Touhy and Lehigh. DO NOT turn left into parking lot from
Touhy heading east, as this is illegal and you may get a traffic
ticket. Enter at the employee entrance on the east side of the
building and register at the guard desk. A valid driver's license
must be presented at the guard desk when registering.
DINNER:
Dinner (optional but please RSVP) will begin at 6:30pm.
Dinner RSVP required - contact Treasurer Riva Oliviera at
riva@motorola.com by Monday, April. 22
Salad and Pizza will be
provided. Please let Riva know if you have a preference for
no-cheese and/or vegetarian.
Price is $10 for non-members and
$8 for members and students.
CHICAGO SECTION
LinkedIn SITE:
A
LinkedIn group has been created for the AES Chicago Section. If
you are a member, and
are interested in joining this group, search groups on
linkedin.com
for “Chicago AES”,
or try using this
link
UPCOMING
MEETINGS:
Tuesday,
April 23rd: Don Keele of Audio
Artistry; at Shure Incorporated
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Recap
Writers Needed. . .
Anyone
interested in helping our section by writing a recap (like the
ones under Past Meeting Recaps)
following one of our meetings, please notify an officer. Recap
writers will get a free
AES coffee mug –
plus
their
work will be published on the AES web site and in the Journal of
the Audio Engineering Society! You can't beat press like that!
Openings
for Presenters / Meeting Ideas
If you or someone you know
is making strides in audio, or you have a meeting idea, please
alert any one of the section officers. We are still organizing
programs for this year's presentations and are looking for
interesting topics.
Join
Email List
The
best way to find out about current and upcoming meetings is our
e-mail distribution. If you'd like your name added to the list,
send a message to Ken
Platz.
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