Past meetings of the Society
January 2010

Happy Holidays to ALL !  

January 2010 Meeting

Date: Thursday, January 14, 2010
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


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.


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*

DIRECTIONS (To Boston College)

Parking is available in the Commonwealth Ave Parking garage for a small price or free on Commonwealth Ave. The entrance to the Walsh Function Room is on the right before the main entrance to Walsh Hall. Look for the AES Banner in the window. I've added an arrow pointing to the entrance on The general directions to Boston College can be found HERE

FROM POINTS NORTH AND SOUTH: Take Interstate 95 (Route 128) to Exit 24 (Route 30). Proceed east on Route 30, also known as Commonwealth Avenue, and follow for about five miles to Boston College.

FROM POINTS WEST: Take the Massachusetts Turnpike (Route 90) to Exit 17. At the first set of lights after the exit ramp, take a right onto Centre Street. Follow Centre Street to the fourth set of lights, and turn left onto Commonwealth Avenue. Follow Commonwealth Avenue 1-1/2 miles to Boston College.

FROM DOWNTOWN BOSTON: Take the Massachusetts Turnpike (Route 90) to Exit 17. Take a left over the bridge after passing the Sheraton Tara Hotel. Take the first right onto Centre Street. Follow above directions from Centre Street.

PUBLIC TRANSPORTATION: The Boston College branch of the MBTA's "Green Line" (B) ends at the Boston-Newton boundary on Commonwealth Avenue


The Boston Audio Society
PO BOX 260211
Boston MA 02126

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updated 2/13/10