JBL Century Gold - Manual (Page 5)

No.
3
The Limited Edition
Century Gold
Bookshelf Loudspeakers set a new
standard for a new century. JBL combines the most advanced technology
with a classic JBL design. These speakers continue the longstanding
tradition of precise studio monitor sound for which JBL is famous. You
will enjoy the benefits of pure titanium dome high-frequency transducers,
cast-frame low-frequency transducers with vented pole pieces, and JBL’s
proprietary Symmetrical Field Geometry (SFG ™ ) magnet design, as well as
high-definition dividing networks incorporating the highest quality
electronic components available.
The
Century Gold
features an all-new 12" (300mm) low-frequency
transducer developed specifically for the
Century Gold
(Figure 1).
Derived from JBL’s legacy of highly powerful yet efficient bass drivers, this
woofer delivers full low-frequency performance with clarity and speed
unprecedented among 12" drivers. The voice coil is 3" (76mm) in diameter
and wound on edge from flat copper ribbon wire to a depth of 0.8" (20mm)
on a thermoset composite ™ form.
The cone is a rigid paper/fiberglass composite, treated with Aquaplas ™ for
strength, speed, and damping. JBL’s Symmetrical Field Geometry is
employed in the form of an aluminum sleeve around the pole piece. This
sleeve reduces second-order distortion through induced flux control. Its
aluminum composition is also a more efficient conductor of heat, so it
assists in dissipating heat away from the voice coil to extend the power
capacity. Cooling of the voice coil is further enhanced by the use of a vented
pole piece. The rigid frame is cast from aluminum alloy, an excellent
thermal conductor, which further acts to efficiently draw heat away from
the voice coil and magnet assembly. This combination of advanced design
technology results in a bass driver that is remarkably free from dynamic
restriction due to heat buildup.
Low-Frequency Transducer
Figure 1 Century 1200
Diecast aluminum
frame for high strength
Matched spider
(to motor for high linearity)
Extended pole
for symmetrical
flux field
0.8" (20mm)
long, 3" (76mm)
diameter edgewound
copper voice coil
for high linearity and
power handling
Thick magnet for high excursion
capability and high flux density
Thick .28" (7mm)
top plate for good
heat sinking,
low magnetic leakage
Aquaplas-
treated
composite cone
Foam
air filter
Heavy aluminum sleeve for
reducing second-order
harmonic distortion due to
flux modulation distortion
Low-Frequency Transducer
final cg om 5-15 7/20/98 1:14 PM Page 3