CBT36K Assembly Manual
The following figure shows several illustrations from the original Navy under-water CBT research papers:
(a)
(b)
(c)
(d)
Fig. 33. Illustrations from the original U.S. Navy technical papers showing a spherical cap (in
red): (a) side view, (b) oblique front view, (c) side view of a 50° spherical cap with “Legendre”
shading (the length of the arrows indicate the strength of the shading which is maximum in
the center of the cap and decreases towards the outside of the cap), and (d) an overlay of
several measured polar curves or beam patterns for the 50° spherical cap radiator shown in
(c). (d) Illustrates the extreme uniformity of the CBT radiator polar curves with frequency.
14.2.6. OVERVIEW of KEELE’S CBT LOUDSPEAKER TECHNOLOGY:
Don Keele applied the technology to loudspeaker arrays in a series of six AES papers between 2000 and
2010 [4-9]. The following illustrates the three different types of CBT loudspeaker arrays that Keele
proposed and analyzed.
(a)
(b)
(c)
Fig. 34. Three types of CBT loudspeaker arrays analyzed by Keele (the red dots indicate
loudspeaker locations): (a) circular spherical-cap array, (b) elliptical toroidal-cap array, and (c)
circular-arc line array.
The first two arrays (a) and (b) control coverage in both planes, while the third array (c) controls coverage
in the vertical plane only but provides wide horizontal coverage. The CBT36 is a circular-arc line array (c)
and is the only type of CBT array considered further in this section.
14.2.7. Free-Standing versus Ground-Plane CBT Line Arrays:
There are two types of CBT line arrays: 1) a free-standing array and 2) a ground-plane array. The free-
standing CBT array can be operated in free space and does not require mounting near any reflecting
surface. The ground-plane CBT array is essentially one half of a free-standing array that is intended to
operate near or very close to a single acoustic reflecting surface, such as a floor, wall, or ceiling. The
reflecting surface essentially doubles the size of the array by recreating the missing half of the array. The
CBT36 is a ground-plane CBT line array. The following figure illustrates a free-standing array and a
ground-plane array with its acoustic reflection along with typical shading values. Shading is explained in
the next section.
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