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JBL Grand Touring Series
subwoofers are available in two
different configurations: as dual
4-ohm voice coils or as dual 2-ohm
voice coils. Depending on the
amplifiers you are using, you may
use GTO subwoofers in singles or
multiples to maximize the power
available from your amplifiers. To
achieve the maximum amplifier
output possible, you should design
a speaker system that provides
the lowest impedance that your
amplifier will drive safely. When
designing a subwoofer system,
consider the following rules:
1. Do not mix different subwoofers
or enclosure types in the same
system. Subwoofers being used in
the same enclosure or powered
from the same amplifier should
be identical models. Mismatched
woofers and enclosures can
result in poor performance from
your subwoofer system.
2. You may connect the coils of a
dual-voice coil woofer in series,
but we recommend that you avoid
connecting separate woofers in
series.
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 can be
calculated using the formula:
Impedance=
1
1
+
1
+
1
...
w
1
w
2
w
3
where w is the nominal
impedance of the woofer.
2. The total system impedance
of voice coils (or woofers) in
series can be calculated using
the formula:
Impedance = w
1
+ w
2
+ w
3
...
The diagrams at right show parallel
and series speaker connections.
NOTE: There are two jumpers
supplied with the woofers to make
connections easier.
Figure 1. Parallel connection
NOTE: The GTO1004D, GTO1204D
and GTO1504D come with both
jumpers installed for a parallel
configuration.
Figure 2. Series connection
NOTE: The GTO1002D, GTO1202D
and GTO1502D come with one
jumper installed for a series
configuration.
3
CONNECTING YOUR SUBWOOFER TO YOUR AMPLIFIER