1500.4 GTi — JBL Car Audio User Guide / Operation Manual

Model
1500.4 GTi
Pages
8
Size
286.28 KB
Type
PDF
Document
User Guide / Operation Manual
Brand
Device
Car Audio
File
15004-gti.pdf
Date

View JBL 1500.4 GTi User Guide / Operation Manual online

A Harman International Company
NMGP/N:323967-001
9/95
GTi Automotive 
Intercooled Subwoofer
Application and Installation Guide
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GTi Subwoofer Owners Manual  7/17/98 9:51 AM  Page 8
Welcome to Club GTi
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.
Autosound at its Best 
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.
Unleash Maximum Performance
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. 
Enclosure Basics
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. 
3
Table of Contents
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
2
Staple or clip your original bill of sale here 
GTi Subwoofer Owners Manual  7/17/98 9:51 AM  Page 2
Welcome to Club GTi
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.
Autosound at its Best 
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.
Unleash Maximum Performance
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. 
Enclosure Basics
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. 
3
Table of Contents
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
2
Staple or clip your original bill of sale here 
GTi Subwoofer Owners Manual  7/17/98 9:51 AM  Page 2
Enclosure Design
Follow the simple steps below to design an
optimum ported box for your GTi driver. 
1. Determine the maximum enclosure size 
available for your installation by measuring 
and multiplying the height x width x depth (in
inches) and then dividing by 1728. This will tell
you exactly how many cubic feet your enclosure
will be.
2. To determine the volume of an irregularly
shaped box, divide the box into sections, calcu-
late the volume of each section individually, then
add the separate volumes to determine the total
box volume. Here are some useful formulas to
help you calculate volumes:
USEFUL FORMULAS
1 cubic foot = 1728 cubic inches
1 cubic foot = 28.32 liters
1 liter = 0.353 cubic feet = 61 cubic 
inches = 1000cm
3
Radius = 1/2 diameter 
Box volume = height x width x depth 
Volume of triangular box section = 1/2 base x
height x length 
Volume of tubular duct = area of circle x length
pi (
π
) = 3.1416 
Area of circle = pi (
π
) x radius
2
Diameter of circle = 2 x area / pi (
π
Area of square = height x width
3. Now that you have calculated the internal box
volume, you should subtract the DRIVER DIS-
PLACEMENT (listed on the specification sheet)
while also subtracting approximately 0.1 cubic
feet for the port tube (if one is being used). If
you’d like, you may calculate the exact dis-
placement of the port tube by utilizing the for-
mula listed above (Volume of tubular duct).  
4. Using the GTi Enclosure chart (shown on your
GTi driver specification sheet), choose a desired
box volume on the vertical chart axis, which fits
within the size limit you have established. Draw
a line across from this point until it intersects the
recommended tuning frequency. Draw a line
down to the horizontal axis and read the corre-
sponding tuning frequency.  We have drawn an
example on the chart.
5. Use the Port Nomograph on the Driver Specifica-
tion sheet to determine the port diameter and
length based on the enclosure volume and tuning
frequency determined in step 4. Follow these
steps to determine the port.
Port Dimension Calculation
1. Draw a line from the chosen enclosure volume to
the desired tuning frequency.  Continue this line
until it intersects with the Lv/Sv construction line
(Lv = port length, Sv = port opening surface
area). This is called the construction point.
2. Draw a horizontal line starting from the con-
struction point straight through the chart. Note
that the Lv/Sv axis also appears at the right of
the chart to help keep your line parallel all the
way across the chart.
3. Select the curved line with the port diameter
you would like to use. Locate the point where
this curved line intersects with your horizontal
construction line and draw a vertical line from
this point down to the bottom of the chart. 
NOTE: Try to use a port tube no smaller than 1/3 the
diameter of your speaker. Using a smaller diameter
port can result in “whistling” or “breathing” noises.
4. The required port length is found at the point
where the vertical line you’ve drawn intersects
with the scale at the bottom of the chart.
NOTE: The recommended port tube dimensions
should be considered a starting point. Since it is
impossible to predict “in-car” response exactly, you
may find that a port length slightly longer or shorter
than that recommended may produce slightly better
results. Experiment! 
Lay out plans for your box using the information
determined in the above steps and the box con-
struction tips listed on page 6. 
5
Vehicle Acoustics
The acoustics of your vehicle also influence
bass performance tremendously. Fortunately, the
small interior volume of most cars and trucks
boosts low bass output enough to allow for small-
er enclosure sizes while still achieving good bass
performance. As a general rule, below 50-80 Hz
(depending on interior size), bass response
increases at a rate which approaches 12dB per
octave as the frequency decreases. This adds a
significant bass reinforcement to the actual output
of the subwoofer. If this rise in bass is not
addressed in the design of your enclosure, bass
performance may be boosted to the point where it
is actually too strong for some tastes. For others,
there is never too much! The enclosure design
recommendations which appear on the specifica-
tion sheet for your particular model, were
chosen for optimum in-car performance.
You may find them to be different than the
recommendations from formulas used to
design enclosures for in-home or profes-
sional sound-reinforcement applications.
These “Transfer Function Compensated”
tuning recommendations result in small
enclosures with excellent in-car low fre-
quency performance.
4
5 Hz
–36
–30
–24
–18
–12
–6
0
6
dB
10
100
Frequency
Normalized Amplitude Response (dB/Hz)
JBL SpeakerShop 1.0
1000
2000
500
50
Enclosure-only response 
Transfer Function 
Compensated Tuning (33Hz)
Vehicle Transfer Function
In Car Response Curve 
This graph shows the result of tuning the enclosure to compensate for the effects 
of the vehicle transfer function. Note that the in-car response is smoother and the 
–3dB point moves down to approximately 22Hz.
5 Hz
–36
–30
–24
–18
–12
–6
0
6
dB
10
100
Frequency
Normalized Amplitude Response (dB/Hz)
JBL SpeakerShop 1.0
1000
2000
500
50
Enclosure-only response with
Standard “Optimum” Tuning (42Hz)
Vehicle Transfer Function
This graph shows the effect of vehicle transfer function added to an enclosure 
using “standard” tuning. Note the peak at 50Hz, with a –3dB point of 
approximately 31Hz.
In Car Response Curve 
5 Hz
–36
–30
–24
–18
–12
–6
0
6
dB
10
100
Frequency
Normalized Amplitude Response (dB/Hz)
JBL SpeakerShop 1.0
1000
2000
500
50
In Car Response with Transfer 
Function Compensated Tuning
In Car Response with 
Standard Tuning
This is a comparison of in-car response curves with and without transfer function 
compensated tuning.
GTi Subwoofer Owners Manual  7/17/98 9:51 AM  Page 4
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Here you can view online or download JBL 1500.4 GTi User Guide / Operation Manual in pdf. This User Guide / Operation Manual can help you recover, restore, fix, disassemble and repair JBL 1500.4 GTi Car Audio. Information contained in JBL 1500.4 GTi service manual (repair manual) typically includes:

  • Disassembly, troubleshooting, programming, maintenance, remote, adjustment, installation and setup instructions.
  • Schematics, wiring and block diagrams.
  • Printed wiring boards (PWB) and printed circuit boards (PCB).
  • Parts list (bill of materials).