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
max
is determined
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.
Figure 3.
JBL dual-gap design
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)
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)
5
CONNECTING YOUR SUBWOOFER TO AN AMPLIFIER
TOP COIL
IN GAP #1
DRIVES CONE
FORWARD
ALUMINUM
COVER
2nd
TOP PLATE
1st
TOP PLATE
POLEPIECE
BOTTOM COIL
IN GAP #2
DRIVES CONE
REARWARD
CONE
SPIDER
GAP #1
GAP #2
MAGNET
JBL
DUAL GAP DESIGN
OVERHANG
DETERMINES
X
max
TERMINAL
JUMPER
INTACT
COILS IN PARALLEL
3 OHMS
TERMINAL
JUMPER
INTACT
+
RED
TERMINAL
BLACK
TERMINAL
TERMINAL
JUMPER
REMOVED
TERMINAL
JUMPER
REMOVED
COILS IN SERIES
12 OHMS
+
RED
TERMINAL
BLACK
TERMINAL