K2S5800 (serv.man2) - JBL Audio User Guide / Operation Manual. Page 8

frequency drivers, it utilizes
forced-air cooling. The entire 
magnetic structure is attached to 
a die-cast aluminum-alloy frame.
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 1200FE has a central cooling
duct which effectively cools the
voice coil and reduces the likeli-
hood of hot spots. By reducing the
operating temperature of the voice
coil, power compression is signifi-
cantly 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 3-inch-diameter
fiberglass former. This configura-
tion 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 han-
dle extremely high power levels
over extended periods of time. The
SonoGlass horn is acoustically
inert and precision-molded to
exacting tolerances. 

Phase Plug

Aluminum

Edge-Wound

Voice Coil

Neodymium

Magnet

Aluminum-
Alloy Cover

75mm 
Pure-
Aluminum
Diaphragm

Binding-
Post Input
Terminal

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

8