JBL MkII automotive Owner's Manual page 5

At extremely high power, each coil will
enter the other coil's magnetic gap. This
will cause magnetic braking, which will
slow the cone's motion and prevent
damage due to overexcursion. For a
GTi Series woofer, X is determined
max
by the amount of voice-coil overhang
between the first and second top plates.
See Figure 3. Thermal power handling is
far superior to a conventional DVC
woofer using voice coils of a similar
diameter and length because Differential
Drive provides twice the heat-dissipating
surface area and two top plates to
transfer heat to the magnet-cover fins.
JBL
DUAL GAP DESIGN
Figure 3. JBL dual-gap design
CONE
TOP COIL
IN GAP #1
SPIDER
DRIVES CONE
FORWARD
1st
GAP #1
TOP PLATE
MAGNET
POLEPIECE OVERHANG
DETERMINES
X
max
2nd
GAP #2
TOP PLATE
BOTTOM COIL
IN GAP #2
DRIVES CONE
ALUMINUM
REARWARD
COVER
CONNECTING YOUR SUBWOOFER TO AN AMPLIFIER
CONFIGURING
THE VOICE COILS
Figure 4. Terminal locations
Note: Unlike conventional DVC
subwoofers, the two sets of terminals
are configured so that both positive (+)
terminals are on one side of the frame
and both negative (–) terminals are on
the other side. GTi Series subwoofers
are shipped with terminal jumpers
installed which configure the two 6-ohm
voice coils in parallel for a 3-ohm load.
Note: Both voice coils MUST be
connected to the amplifier in series
or parallel.
Figure 5. Connecting the voice coils in
parallel (3 ohms)
TERMINAL TERMINAL
JUMPER JUMPER
INTACT INTACT
RED BLACK
TERMINAL TERMINAL
+
COILS IN PARALLEL
3 OHMS
Note: Connect the coils in parallel if you
are connecting a single woofer to an
amplifier.
Figure 6. Connecting the voice coils in
series (12 ohms)
TERMINAL
TERMINAL
JUMPER
JUMPER
REMOVED
REMOVED
RED BLACK
TERMINAL TERMINAL
+
COILS IN SERIES
12 OHMS
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