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03
JBL GTp subwoofers are available
in two different configurations:
single 4-ohm voice coil and dual
4-ohm voice coils. Depending on
the amplifier you are using, you
may use either single-voice-coil
or dual-voice-coil subwoofers in
singles or multiples to maximize
the power available from your
amplifier. To achieve the maximum
amplifier output possible, you
should design a speaker system
that provides the lowest impedance
that your amplifier is rated to
drive safely. When designing a
subwoofer system, consider the
following rules:
1. Don’t mix different subwoofer
or enclosure types in the same
system (use all single-coil
woofers or all dual-coil woofers).
2. You may connect the coils of a
dual-voice-coil woofer in series,
but NEVER connect separate
woofers in series. Because the
amplifier-damping factor (the
amplifier’s ability to control the
motion of the woofer) is
expressed as a ratio of terminal
impedance (the sum of speaker
impedance, wire resistance and
the D.C. resistance of any
crossover coil connected to the
woofer) to amplifier-output
impedance, connecting separate
woofers in series reduces the
damping factor of the amplifier
to a value less than 1. This will
result in poor transient response.
3. You must use both coils of a
dual-voice-coil woofer connected
either in series or in parallel.
4. Most amplifiers deliver exactly
the same amount of power
bridged into a 4-ohm load
as they do running a 2-ohm
stereo load.
To design a subwoofer system
that maximizes available amplifier
power, keep the following rules
in mind:
1. The total system impedance of
woofers in parallel = 1/(1/w
1
+
1/w
2
+ 1/w
3
...), where w is the
nominal impedance of the
woofer.
2. The total system impedance
of voice coils (or woofers) in
series = w
1
+ w
2
+ w
3
...
The diagrams below and at right
show parallel and series speaker
connections.
Figure 1. Parallel connection
Figure 2. Series connection
POS ( + )
NEG ( – )
RED
STRIPE
POS ( + )
BLACK
STRIPE
NEG ( – )
POS ( + )
NEG ( – )
RED
STRIPE
POS ( + )
BLACK
STRIPE
NEG ( – )
Connecting Your Subwoofer to Your Amplifier JBL Pro Power GTp Series
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