1800.4 GTi (serv.man2) - JBL Car Audio User Guide / Operation Manual. Page 3

Thank you for purchasing one of the finest

automotive subwoofers that JBL has ever pro-
duced. As a GTi competition series owner, you are
a member of a select group of people who enjoy
the most advanced mobile audio products avail-
able. We call this group “Club GTi.” By sending in
the customer information card, that you will find
packaged with this product, we will automatically
register you as a Club GTi member which will give
you access to exclusive Club GTi apparel and
other special offers we will make available from
time to time. We suggest you fill the card out at
your earliest convenience.

Also, be sure to save your sales receipt in a

safe place. It will be necessary to use this docu-
ment as proof of purchase should you need war-
ranty service.

The GTi Subwoofer is built to meet the same

rigorous standards of construction and perfor-
mance that have long established JBL’s renowned
home and professional speaker systems. The GTi
Subwoofer achieves its exceptional performance
with leading edge technologies that push the per-
formance envelope in automotive sound.

The exceptional sound of the GTi Subwoofer

comes from an Aquaplas coated fiber cone for
extra stiffness and resonance elimination. The

cone motion is controlled by a synthetic rip-stop
suspension which resists tearing for safe, effortless
high-power use. The cone is driven by a massive
motor structure utilizing a 3" or 4" edge-wound
OFC copper wire, high temperature fiberglass,
voice coil. This motor structure includes JBL’s
patented Symmetrical Field Geometry (SFG) to
create a uniform magnetic flux field through the
coil and thus lower distortion. The frame and cone
are contained in a high strength die-cast aluminum
frame for maximum rigidity and higher magnetic
energy concentration on the coil.

What does all this technology add up to? A

driver with smooth frequency response, excellent
transient response, high output efficiency and high
power handling in a rugged package able to deal
with the rigors of high performance car audio. The
result is exceptionally powerful, dynamic and accu-
rate sound reproduction that cuts through the road
noise and provides a solid musical foundation.

Because this is a high performance product

which may be used in many different configura-
tions, we strongly recommend that you have the
subwoofer professionally installed to unleash its
full performance potential. However, if you feel
you have the skills necessary to build a subwoofer
box, read the following information on enclosures
before proceeding. 

The enclosure you build plays a profound role in

the performance of your subwoofer. The size and vent
tuning frequency, where applicable, determine the
low-frequency performance and output capability of
the subwoofer system. Your GTi subwoofer will pro-
vide excellent performance when used in Sealed,
Vented, Infinite Baffle, and Band-pass applications
that are properly designed. Each of these applications
have limits and advantages that should be considered.

GTi woofers are most commonly used either in

Vented enclosures or Infinite Baffle. Instructions which
follow will give you a simplified design method to build
a Vented enclosure for your subwoofer. Another
option is the Infinite Baffle (free air) installation which
doesn’t require complex design and construction, and
can sound very good when solidly installed. However,
because there is no enclosure to control cone motion,
the power handling and maximum output level of an
Infinite Baffle installation is reduced from that of a
Vented enclosure. Refer to the “Points on Power
Handling” section for more information.

For more complex designs, such as single and

dual-vented Band-pass types, we suggest you opti-
mize your design with JBL SpeakerShop, a speaker
system design software for a P.C. running Microsoft
Windows, available from your JBL dealer. If JBL
SpeakerShop or a similar program is not available,
the JBL Customer Service department will be happy
to assist you. 

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Welcome to Club GTi . . . . . . . . . . . . . . . . . . . . . . . 3
Autosound at its Best . . . . . . . . . . . . . . . . . . . . . . . 3
Unleash Maximum Performance. . . . . . . . . . . . . . . 3
Enclosure Basics . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Vehicle Acoustics . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Enclosure Design. . . . . . . . . . . . . . . . . . . . . . . . . . 5
Enclosure Construction Tips . . . . . . . . . . . . . . . . . . 6
Points on Power Handling . . . . . . . . . . . . . . . . . . . 6
Speaker Connection and Combination . . . . . . . . . . 7

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Staple or clip your original bill of sale here 

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GTi Subwoofer Owners Manual  7/17/98 9:51 AM  Page 2