JBL CENTURY GOLD User Manual / Operation Manual ▷ View online
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
frame for high strength
Matched spider
(to motor for high linearity)
(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
top plate for good
heat sinking,
low magnetic leakage
Aquaplas-
treated
composite cone
treated
composite cone
Foam
air filter
air filter
Heavy aluminum sleeve for
reducing second-order
harmonic distortion due to
flux modulation distortion
reducing second-order
harmonic distortion due to
flux modulation distortion
Low-Frequency Transducer
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The
Century Gold
also features an all-new 5" (127mm) mid-frequency
transducer developed specifically for the
Century Gold
(Figure 2). The
voice coil is 2" (50mm) in diameter and wound on edge from flat aluminum
ribbon wire to a depth of precisely .4" (11mm) on a thermoset composite
™
form. The cone is made of Kevlar
®
with a composite rubber/vinyl surround.
Kevlar was chosen for the cone material because it is extremely strong and
rigid while relatively low in mass. This allows the driver to move fast
enough to reproduce the dynamics of the critical midrange frequencies while
retaining the low distortion characteristics necessary for accurate musical
reproduction. Its very high power capability and freedom from breakup
make it an ideal midrange in a system that is designed to play at high levels
with absolutely no signs of distress. It makes the transition from the woofer
at 600Hz, providing good dispersion throughout the important vocal range.
Throughout the history of high-frequency transducer design, the goal of
extended frequency response has been at odds with the need for high
power handling. JBL has long chosen titanium as the material for its
highest quality high-frequency transducers and the
Century Gold
is
no exception (Figure 3). Titanium possesses the essential requirements for
a high-frequency transducer. First, titanium is extremely light yet rigid.
The goal is to maintain a piston-like action as high in frequency as possible.
If the material flexes easily, the diaphragm will break up into random
vibrations. Second, titanium is virtually free from fatigue. The material
is virtually immune from the cumulative effects of millions of flexures
over long operating periods. These factors, coupled with the higher power
handling that titanium affords, allow us to produce an extremely smooth
high-frequency transducer with extended frequency response that can handle
all the demands of today’s digital programs.
High-Frequency Transducer
No.
4
1
"
copper
voice coil
provides
smooth
performance
and high
power
handling
provides
smooth
performance
and high
power
handling
Cast zinc faceplate
for less resonance
for less resonance
Titanium dome
Figure 3 050 Gold
High-Frequency Transducer
Mid-Frequency Transducer
Diecast aluminum frame
for high strength
for high strength
Rubber/vinyl
surround
surround
Vented pole piece allows
driver to run cooler
driver to run cooler
Neodymium magnet provides
high flux density with low mass
high flux density with low mass
0.4" (11mm) long,
2" (50mm)
diameter edgewound
aluminum voice coil for
high linearity and
power handling
2" (50mm)
diameter edgewound
aluminum voice coil for
high linearity and
power handling
Kevlar
cone
cone
Figure 2 Century 500
Mid-Frequency Transducer
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The job of the dividing network is to distribute the various frequencies to
their respective transducers. The network is also designed to complement
component location on the baffle. Slopes are chosen to match the exact
response of each driver in its respective frequency range, as well as to
ensure that the high-frequency transducers are adequately protected from
dangerous low-frequency components.
For the
Century Gold
system, we chose our Charge-Coupled Linear
Definition
™
Dividing Network. The inductors are all designed for high-
current, low-distortion operation. All capacitors in the network are
series/parallel connected and operated with D.C. bias. This effectively
enables the capacitors to operate in “Class A” mode, which substantially
increases sonic detail, resolution, and dynamics. The low-frequency section
of the dividing network is mounted on a dedicated circuit board that
separates both electrical and magnetic properties from that of the
midrange and tweeter sections.
Additionally, the
Century Gold’s
dividing network allows for passive,
bi-wire, passive bi-amp, and full active bi-amp operation. For the full active
bi-amp mode we recommend the use of a high-quality electronic crossover.
Dividing Networks
No.
5
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The battery should be replaced approximately every 2 years. This is
accomplished as follows:
•
Unscrew the two screws that hold the battery access cover in place. It
is located on the upper portion of the dividing network, on the rear of
the speaker enclosure (Figure 4).
•
Write today’s date, including the year, in this manual.
•
Install the battery by aligning the battery terminals with the mating
terminals in the network housing. Align male to female, female to
male terminals, then snap the connectors together, assuring a tight
connection.
•
Replace the battery access cover and install screws.
Battery Replacement Record
Date Installed:
No.
6
Battery Replacement
BATTERY
BI-AMP
High Frequency
Low Frequency
NORMAL/
BI-WIRE
BI-WIRE
Figure 4 Battery Installation
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Click on the first or last page to see other CENTURY GOLD service manuals if exist.