JBL Century Gold manual Low-Frequency Transducer, Matched spider To motor for high linearity

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Figure 1 Century 1200 Low-Frequency Transducer

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.

Low-Frequency Transducer

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

Matched spider

(to motor for high linearity)

Diecast aluminum frame for high strength

Heavy aluminum sleeve for reducing second-order harmonic distortion due to flux modulation distortion

Extended pole for symmetrical flux field

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

Foam air filter

Aquaplas- treated composite cone

Thick .28" (7mm) top plate for good heat sinking,

low magnetic leakage

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

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.