K2S4800 (serv.man2) - JBL Audio User Guide / Operation Manual. Page 6

This provides accurate, rigid
support for the motor and cone
mounting points, as well as
doubling as a massive heatsink by
providing a huge surface area for
heat dissipation.

The 1500FE has a central cooling
duct that effectively cools the voice
coil and reduces the likelihood of
hot spots. By reducing the
operating temperature of the voice
coil, power compression is
significantly reduced, which
enables the low-frequency driver to
operate in a more linear fashion
over a wider sound pressure level
(SPL) range. 

The voice coil itself is constructed
from edge-wound aluminum wire
on a massive 4-inch-diameter
fiberglass former. This
configuration provides for further
cooling ability in conjunction with
the motor design.

The Aquaplas-coated, Kevlar-
composite cone, along with the 
EPDM rubber surround, provides
excellent damping and transient
response characteristics.

See Figure 4.

The 435AL neodymium high-
frequency compression driver is
based on the professional JBL 2430
device. It incorporates a rare-earth
neodymium magnet structure,
designed by extensive computer
modeling, including finite element
analysis, which combines the
attributes of efficiency, strength,
low mass and compact size. This
motor structure is coupled with 
a 3-inch aluminum diaphragm.
Aluminum provides improved low-
distortion characteristics and flat
frequency response. 

High-temperature materials and
adhesives allow the driver to
handle extremely high power levels
over extended periods of time. The
SonoGlass horn is acoustically inert
and precision-molded to exacting
tolerances. 

Figure 4. Cutaway view of 435AL high-frequency transducer.

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