JBL Synthesis K2 S9900 - Manual (Page 14)

14
High-Current and
Fatigue-Resistant
Pigtail Leads
Extruded-Aluminum
Spider Spacer
Dual Inverted
Nomex Spiders
Cone Body:
Special Paper-
Pulp Composite
VGC – Vented Gap
Cooling Channels
Voice Coil:
Aluminum Ribbon Wire on
High-Temp Fiberglass Former
Dust Dome:
Paper-Pulp Composite
EPDM-Foamed
Rubber Surround
Glass-Filled ABS
Terminal Base
5-Way Gold-Plated
Terminal Posts
Conductive Ring:
Extruded 6063
Aluminum
Magnet:
Alnico 5DG
Pot:
SAE-1008
Polepiece:
SAE-1008 Steel
Gap Sleeve:
SAE-1008 Steel
Rear Cover:
Cast 380 Aluminum
Copper and Steel
Gap Ring Laminations
Frame:
Cast 380 Aluminum
Figure 3. 1500AL-1 section view.
The 1500AL-1 low-frequency driver is a 15-inch (380mm)-diameter device with
a 4-inch (100mm) voice coil completely immersed in a radial field generated by
an alnico 5DG magnet. Alnico was chosen because of its stable operating point.
This material is insensitive to temperature changes and back EMF from the coil.
JBL engineers have overcome the tendency of alnico to demagnetize with high
drive, by utilizing a massive shorting ring at the base of the motor assembly. The
top plate is constructed of alternating copper-steel laminations. The presence of
the copper rings linearizes the magnetic properties of the gap to all but eliminate
eddy current distortion.
The outer suspension is made of EPDM-foamed rubber, which has the longevity
and frequency response characteristics of traditional rubber surrounds, but with
a low density very close to that of foam surrounds. Low-loss EPDM material
was chosen so that the transient detail of musical signals could be preserved.
Dual inverted Nomex
® spiders are employed for the cancellation of even-order
distortion components. All suspension elements are tailored for maximum
mechanical displacement linearity.
The cone consists of a special layered paper-pulp matrix with proprietary
Aquaplas damping, which offers more pistonic behavior throughout the
woofer’s operating bandwidth, and controlled cone breakup beyond it.