JBL GT4 User manual

Automotive Subwoofers Owner’s Manual GT4-10 GT4-12 GT4-15
GT4 SERIES™
Owner’s Manual
Einbauanleitung
Guide d’utilisation
Manual del propietario
Gebruikershandleiding
Manuale utente
Bruksanvisning
Omistajan käsikirja
Manual do utilizador

1
Thank you for purchasing a
new JBL GT4 Series subwoofer.
Subwoofer installation requires
woodworking skills and some
experience disassembling and
reassembling automotive interiors. If
you lack the tools or necessary
skills, have your subwoofer installed
by an authorized JBL dealer.
Warning: Playing loud music in
an automobile can permanently
damage your hearing as well as hin-
der 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.
GT4 Series subwoofers are opti-
mized to perform best in small,
sealed, vented and prefabricated
bandpass enclosures. While infinite-
baffle mounting of GT4 Series subs
is possible, 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 GT4 Series sub-
woofers.
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, 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. If you are using a small
amplifier, a vented box will provide
more 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.
Bandpass 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 bandpass enclosure.
Bandpass-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 enclosure described in the
enclosure design sheet included
with this woofer. Fortunately, there
are many prefabricated bandpass
boxes available and they are all
optimized to extract the most
output possible from any woofer.
Bandpass enclosures can be quite
large and may require a lot of space
inside your vehicle.
Choosing an Enclosure JBL GT4 Series

2
Connecting Your Subwoofer to Your Amplifier JBL GT4 Series
JBL GT4 Series subwoofers are
single 4-ohm voice coil. Depending
on the amplifiers you are using, you
may want to use either one or sev-
eral subwoofers in the same enclo-
sure to maximize the power avail-
able from your amplifiers. To achieve
the maximum amplifier output possi-
ble, 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.
2. We recommend that you avoid
connecting separate woofers in
series. 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. Therefore, 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. 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 ...
w1w2w3
where w is the nominal
impedance of the woofer.
2. The total system impedance
of woofers in series can be calcu-
lated using the formula:
Impedance = w1+ w2+ w3...
The diagrams at right show parallel
and series speaker connections.
Figure 1. Parallel connection
POS ( + )
NEG ( – )
RED
STRIPE
POS ( + )
BLACK
STRIPE
NEG ( – )
Figure 2. Series connection
POS ( + ) NEG ( – )
RED
STRIPE
POS ( + )
BLACK
STRIPE
NEG ( – )

3
GT4-10 GT4-12 GT4-15
10" Automotive 12" Automotive 15" Automotive
subwoofer subwoofer subwoofer
Power handling (RMS) 250 Watts 250 Watts 250 Watts
Power handling (Peak) 1000 Watts 1000 Watts 1000 Watts
Sensitivity (2.83V/1m) 90dB 93dB 91dB
Frequency response 28Hz – 500Hz 23Hz – 450Hz 20Hz – 400Hz
Impedance 4 Ohms 4 Ohms 4 Ohms
Mounting depth 147mm 159mm 172mm
Cut-out diameter 232mm 283mm 362mm
Features, specifications and appearance are subject to change without notice.
JBL Consumer Products • 250 Crossways Park Drive, Woodbury, NY 11797
1.800.336.4JBL (4525) • www.jbl.com
Europe: 2, route de Tours. 72500 Chateau-du-Loir
©2003 JBL, Incorporated • JBL is a registered trademark of JBL, Incorporated
Part No. GT4SUBSEROM
Specifications JBL GT4 Series
Declaration of Conformit
We, Harman Consumer International
2, route de Tours
72500 Chateau-du-Loir
FRANCE
declare in own responsibilit , that the products described in this owner’s manual are in
compliance with technical standards:
EN 50081-1:1992
EN 50082-1:1997
Emmanuel Millot
Harman Consumer International
Chateau-du-Loir, FRANCE. 2/03