JBL GT5-12 User manual

THANK YOU
for purchasing a JBL®GT Series™subwoofer. Subwoofer
installation requires woodworking skills and some experience
in disassembling and reassembling automotive interiors. If
you lack the tools or necessary skills, have your subwoofer
installed by an authorized JBL dealer.
GT SERIES™
GT5-12
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2
2
CHOOSING AN ENCLOSURE
WWAARRNNIINNGG::Playing loud music
in an automobile can permanently
damage your hearing, as well as
hinder your ability to hear traffic.
We recommend listening at low
levels while driving. JBL accepts no
liability for hearing loss, bodily injury
or property damage resulting from
use or misuse of this product.
GT Series subwoofers are optimized
to perform best in small, sealed,
vented and prefabricated band-pass
enclosures. While infinite-baffle
mounting of GT Series subs is possi-
ble, power handling will be greatly
compromised because there’s no
enclosed volume of air to prevent
the speaker’s cone from moving
past its limit. For this reason, we
do not recommend infinite-baffle
mounting for GT Series subwoofers.
You should choose the enclosure
you will use based on the type of
music you listen to, how much
amplifier power you will use for the
subwoofer and how much space
inside the vehicle you can devote
to a subwoofer enclosure.
Because a sealed enclosure
provides the most control over
the woofer’s movement, a woofer
mounted in a sealed enclosure will
handle more power than a woofer
mounted in another enclosure type.
Sealed enclosures provide more-
accurate sonic reproduction than
other enclosure types when
mounted inside a vehicle, so they
are well suited to all types of music.
Sealed-enclosure construction is
straightforward, and there are many
prefabricated sealed enclosures
available. An optimum sealed
enclosure is always smaller than
other types of enclosures optimized
for a particular speaker, so they
require the smallest amount of
space inside the vehicle.
Vented enclosures provide better
efficiency in the 40Hz – 50Hz range,
but this efficiency comes at the
expense of sound in the lowest
octave (below 40Hz) and at the
expense of some control and power
handling at the lowest frequencies.
If you are using a small amplifier,
a vented box will provide more
perceived bass output from less
power. Vented enclosures are also
well suited to a variety of music
types. Because vented enclosures
require the volume of the enclosure
and the size of the port to have
a specific relationship with the
characteristics of the woofer, the
enclosure must be built exactly to
the specifications provided. While
there are some prefabricated
vented boxes available, matching
a prefabricated box to a particular
woofer is difficult. If you wish to
use a vented enclosure, we strongly
recommend having your authorized
JBL dealer build it or verify that your
design is correct if you wish to build
it yourself. An optimum vented
enclosure is always larger than the
optimum sealed box for the same
woofer and will require more space
inside the vehicle.
Band-pass enclosures often provide
the most output available from any
amplifier and subwoofer combination,
at the expense of sonic accuracy.
If sheer SPL (sound-pressure level)
is what you desire most, choose a
band-pass enclosure. Band-pass-
enclosure design is very tricky, and
the aid of a computer and enclosure
design software is necessary. If you
are an experienced installer or have
some woodworking experience,
you may wish to build the band-pass
enclosure described in the enclosure
design sheet included with this
woofer. Fortunately, there are many
prefabricated band-pass boxes
available, and they are all optimized
to extract the most output possible
from any woofer. Band-pass
enclosures can be quite large and
may require a lot of space inside
your vehicle.

The GT5-12 subwoofer has a single
4-ohm voice coil. Be sure to consider
your amplifier’s optimum load when
designing a subwoofer system. Many
bridgeable 2-channel amplifiers are
optimized to drive a single 4-ohm
woofer in bridged mode. If you will
use multiple woofers, be sure to
configure them to extract all the
power available from your amplifier.
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
by the same amplifier should
be identical models. Mismatched
woofers and enclosures can
result in poor system performance.
2. Most amplifiers deliver exactly
the same amount of power
bridged into a 4-ohm load
as they do driving a 2-ohm
stereo load.
3. If you are designing a multiple-
woofer system, be sure to configure
the woofers so that they each
receive the same amount of
power from the amplifier. Never
connect two identical woofers in
series and then connect that pair
to another woofer in parallel. If
your system will include an odd
number of woofers, be sure to
connect all the woofers in either
series or parallel according to
the rules that follow, in order to
maximize the power available
from your amplifier:
a. The total system impedance
of voice coils (or woofers) in
series can be calculated using
the formula:
Impedance = w1+ w2+ w3...
b. The total system impedance
of woofers in parallel can be
calculated using the formula:
Impedance = 1
1+1+1...
w1w2w3
where w is the nominal
impedance of the woofer.
The diagrams at right show series
and parallel speaker connections.
Figure 1. Connecting two woofers
in series to the amplifier (8 ohms)
Figure 2. Connecting two woofers in
parallel to the amplifier (2 ohms)
3
3
CONNECTING YOUR SUBWOOFER TO YOUR AMPLIFIER
Red
Positive
Black
Negative
Red
Positive
Black
Negative
Red
Positive
Black
Negative
Red
Positive
Black
Negative
Red
Positive
Black
Negative
To Amp
Positive
To Amp
Negative
To Amp
Positive
To Amp
Negative
To Amp
Positive
To Amp
Negative
Series connection of two woofers (8 ohms)
Parallel Connection of two woofers (2 ohms)
Connection of single woofer (4 ohms)
Red
Positive
Black
Negative
Red
Positive
Black
Negative
Red
Positive
Black
Negative
Red
Positive
Black
Negative
Red
Positive
Black
Negative
To Amp
Positive
To Amp
Negative
To Amp
Positive
To Amp
Negative
To Amp
Positive
To Amp
Negative
Series connection of two woofers (8 ohms)
Parallel Connection of two woofers (2 ohms)
Connection of single woofer (4 ohms)

Declaration of Conformity
We, Harman Consumer Group International
2, route de Tours
72500 Château du Loir
France
declare in own responsibility that the product described in this owner’s
manual is in compliance with technical standards:
EN 61000-6-3:2001
EN 61000-6-1:2001
Klaus Lebherz
Harman Consumer Group International
Château du Loir, France 4/07
Harman Consumer Group, Inc.
250 Crossways Park Drive, Woodbury, NY 11797 USA
516.255.4JBL (4525) (USA only) www.jbl.com
© 2007 Harman International Industries, Incorporated. All rights reserved.
JBL is a trademark of Harman International Industries, Incorporated,
registered in the United States and/or other countries. GT Series is a
trademark of Harman International Industries, Incorporated.
Part No. GT5-12OM4/07
www.jbl.com
SPECIFICATIONS
GT5-12
12" (300mm) Single 4-Ohm Subwoofer
Power Handling, RMS 275W
Power Handling, Peak 1100W
Sensitivity (2.83V/1m) 93dB
Frequency Response 23Hz – 450Hz
Impedance 4 Ohms
Mounting Depth 6-7/16" (164mm)
Cutout Diameter 11-1/4" (286mm)
Overall Diameter 12-5/16" (313mm)
A valid serial number is required for warranty coverage.
Features, specifications and appearance are subject to change without notice.
These products are designed for mobile applications and are not intended for connection to the mains.