JBL 508GTI User Manual

408GTi 508GTi
AUTOMOTIVE NEO/KEVLAR MATCHED
COMPONENT SYSTEM WITH CAST FRAME
INSTALLATION GUIDE

Table of Contents

Welcome to Club GTi.........................................................................3

About this Manual ..............................................................................3

Autosound at its Best .........................................................................3

Designing Your System......................................................................4

Component Placement.......................................................................5

Installation Warnings and Tips ...........................................................5

Mounting Instructions.........................................................................6

Installing the GTi System Crossover..................................................6

Woofer/Midrange Driver Mounting .....................................................7

Mounting the 408 and 508GTi Tweeter..............................................8

Tweeter Surface Mounting Instructions..............................................8

Tweeter Surface Angle Mounting Instructions....................................9

Tweeter Flush Mounting Instructions ...............................................10

Tweeter Flush Angle Mounting Instructions......................................11

Wiring...............................................................................................12

Crossover Tweeter Level Adjustment...............................................12

System Connections ........................................................................13

Speaker Break-In .............................................................................14

A Note on Power Handling ...............................................................14

In Case of Difficulty ..........................................................................14

Specifications...................................................................................16

Thiele-Small Specifications..............................................................17

Mounting Templates.........................................................................19

2

Welcome to Club GTi

About This Manual

Autosound at its Best

Thank you for purchasing the finest
Automotive Component Systems JBL has
ever produced. As a GTi Competition
Series owner, you are a member of a
select group of people who enjoy the most
advanced mobile audio products available.
We call this group “Club GTi.” By sending
in the customer information card, which
you will find attached to your warranty, 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 document as proof of purchase
in the event that you ever need warranty
service. It is also useful for insurance
purposes and for establishing value when
you re-sell your vehicle.

Because of the performance capability
of your GTi Competition Series product,
and the variety of potential system
configurations, we strongly recommend
that you have the system professionally
installed. You will also get a better warranty
if your equipment is professionally installed
by an authorized GTi dealer and you have
your warranty card stamped. This manual
provides information on installation and
usage to help a skilled technician get the
most from your GTi Competition Series
product. This manual does not cover basic
information about installation which is
common knowledge to a professional
installer, except for information which is
unique to the 408 and 508GTi systems.

If you feel you possess the necessary
skills, and prefer to install the equipment
yourself, this manual will provide you with
the necessary specifics to properly use the
408 or 508GTi in typical installations.
Consult your JBL dealer, or a qualified
technician, for more information.

The 408 and 508GTi systems are built
to meet the same rigorous standards of
construction and performance that have
long established JBL’s renowned home
and professional speaker systems. The
408 and 508GTi Woofer/Midranges
incorporate advanced JBL woven Kevlar
cones which are especially suited to the
unique acoustic and environmental
conditions which characterize automotive
sound. The 408 and 508GTi Tweeter
incorporates advanced JBL pure titanium
technology which is especially suited to
the unique acoustic environment of
modern vehicles. The 408 and 508GTi
have been engineered to provide excellent
power handling, good dispersion and
balanced frequency response, along with
minimum size and flexible installation
options for optimizing placement within the
vehicle.

The small size of the GTi Drivers is
made possible through the use of a
Neodymium magnet assembly with JBL’s
Stray Field Containment Geometry. By

3

minimizing stray magnetic fields, this
closed circuit magnetic assembly design
concentrates the magnetic field on the
voice coil where it provides superior
performance. In the woofer/midrange
drivers, this high concentration of magnetic
power is coupled to a 2" Edge-wound
Aluminum Wire Voice Coil on a High
Temperature Fiberglass Former . This voice
coil uses lightweight aluminum wire to
maintain the agility to reproduce high
frequencies while its large diameter and
fiberglass former assures extremely high
thermal power handling.

Treated Kevlar fiber cones are used
because of their combination of low
weight, high stiffness and resistance to
resonances. The 408 and 508GTi
Woofer/Midranges are topped off with a
treated fabric inverted dome for smooth
reproduction of upper midrange
frequencies.

The cone motion of these high
excursion designs is controlled by a
Aromatic Polyamid Fiber Spider. This new
material is able to control the 0.6" motion
of the cone while maintaining musical

4

accuracy because it is 3 times stronger
than conventional spider materials.

The tweeters in the 408 and 508GTi
feature domes made from pure titanium.
Pure titanium has long been known to have
a very high stiffness to weight ratio, making
it ideal for treble reproduction. However,
only JBL has “tamed” titanium through a
special manufacturing process. The dome
of the 408 and 508GTi Tweeter is created
using special nitrogen gas cooled forming
machines which can create a uniformly
paper-thin dome without the work­hardening or deformation which causes
resonances in domes made without benefit
of this process

Equally important is the 408 and
508GTi crossover design. Each crossover
was meticulously optimized in JBL’s state­of-the-art acoustic laboratory to guarantee
a seamless blend of the woofer/midrange
and tweeter output. Unlike generic or
general purpose crossovers, the design of
the 408 and 508GTi Crossovers was
performed with a full knowledge of the
performance characteristics of each driver,
allowing frequency, phase, and power

response to be completely optimized for
each combination.

What does all this technology add
up to? Asystem with ideal frequency
response, excellent off axis response,
and high output capability all in a small
and elegant package. The result is
exceptionally smooth and detailed music
reproduction over the full range of
frequencies and clean sound that cuts
through road noise.

Designing Y our System

The overall quality of any system
design is a result of how well all of the
components work together, not just the
result of the performance of any one
component. JBL GTi Series woofer/
midbass or subwoofer transducers are
the ideal companion products to your 408
and 508GTi systems. Each of the GTi
Competition Series products are designed
to complement the others to provide the
highest performance with the simplest and
most predictable system design. To use the
408 and 508GTi as the woofer/midrange

and high frequency transducers in a high
quality system, we recommend you use
either a high quality active crossover
such as JBL’s GTX47, GTX4 or GTX2
to provide optimum matching to your
subwoofer or woofer/midbass loudspeaker.
If you prefer passive crossovers, we
recommend that you use only high quality
audiophile grade film-type capacitors
and Low DCR inductors to get the most
out of your system. The most popular
system configuration is a hybrid using
an active crossover for the subwoofer to
woofer/midrange crossover point, and a
passive crossover for the woofer/midrange
to tweeter crossover. Your GTi Competition
Series Dealer is uniquely qualified to help
guide you on the best system configuration
for your needs.

Component Placement

The location of each of the
loudspeakers plays a vital role in achieving
proper frequency response and spacious
imaging. Because the 408 and 508GTi
systems have an extremely wide and

smooth dispersion pattern, excellent
performance may be achieved in any
vehicle. Due to the wide variety of vehicles,
there is not one “right” way to locate the
408 and 508GTi, however knowledge of
the following considerations will help you
get the most from your system:

1. The most spacious stereo image is
achieved when the speakers are placed
as wide apart as possible.

2. The best center image will be achieved
when the distance from the left speaker
to your left ear is as equal as possible to
the distance from the right speaker to
your right ear. This is most easily
achieved by placing the 408 or
508GTi as far forward as you can.

3. The best system integration is achieved
when the woofer/midrange is mounted
close to the tweeter. Installing the
tweeter close to the woofer/midrange
helps smooth the transition from
woofer/midrange to tweeter at the
crossover point.

4. Y ou will get the best frequency
response when the path from the
speakers to your ear is unobstructed.

5. Because of the high acoustic energy
capability of the 408 and 508GTi, the
woofer/midrange drivers must be
securely mounted in a rigid panel which
is free from resonances, rattles and air
leakage.

Installation Warnings and Tips

• Be careful not to cut or drill into fuel
tanks, fuel lines, brake or hydraulic
lines, vacuum lines or electrical wiring
when working on your vehicle. Inspect
behind panels before you cut or drill.

• Be sure to check for clearance of
window, cranks and linkages when
mounting speakers in door panels.

• Do not use the speakers unmounted.
Failure to securely mount this product
could result in damage or injury,
particularly in the event of an accident.

• Although the materials used on the 408
and 508GTi are inherently water
resistant, do not mount the speakers
where they will get wet.

• Always disconnect the ground wire
from the battery before doing any work
on the vehicle.

5

Mounting Instructions

Pick a mounting location after reading
the recommendations in the Component
Placement section of this manual.

Installing the GTi System
Crossover

The GTi system crossover should be
mounted securely to prevent damage to
the crossover or possible loosening of
wiring connections. Choose one of the
crossover mounting methods and follow
the directions below:

2. Remove the crossover board from the
plastic case.

3. Use wire ties to secure the plastic case
to the desired location as shown in
Figure A.

4. Cut off the excess plastic on the wire ties.

5. Re-install the PCB and install wiring
from the crossover to the amplifier
and speaker locations as shown in
Figure K.

6. Re-install the crossover cover.

Figure B

3. Mark 4 hole locations, drill holes and
secure the bottom cover to the desired
mounting location as shown in Figure B.
Before starting make sure no electrical
or other critical car components are
located where you will be drilling.

4. Re-install the PCB and install wiring
from the crossover to the amplifier
and speaker locations as shown in
Figure K.

5. Re-install the crossover cover.

Note: Do not mount the GTi Crossover in a

location where it can get wet, as this
may cause damage to its components.

MOUNTING RING
ADAPTER

Figure A

Mounting the GTi Crossover with Wire Ties

1. Remove the crossover cover as shown
in Figure L.

6

Mounting the GTi Crossover with Screws

1. Remove the crossover cover as
shown in Figure L.

2. Remove the crossover board from the
plastic case.

Figure C

WOOFER/
MIDRANGE

Woofer/Midrange Driver

FABRIC
DISPLACEMENT
RING

WOOFER/
MIDRANGE

Mounting

Mounting the Woofer/Midrange to
Stock Hole Locations

1. Access the stock speaker location and
remove the stock speaker. The 408
and 508GTi include mounting ring
adapters which allow the speaker to
be mounted in standard 4" and 5
holes respectively.

2. Attach the mounting ring adapter to
the stock location using four #8 x 1
screws as shown in Figure C.

3. Attach the foam gasket to the back of the
woofer/midrange. Connect the speaker
wire from the crossover terminals marked
“W” to the speaker by either soldering
(preferred) or using crimp terminals.
Connect the wire from the “W+” terminal
on the crossover to the red “W” terminal
on the woofer/midrange. Repeat the
same process for the “W–” terminal (see
Figure K for details).

4. Mount the woofer/midrange driver to
the adapter ring using three #8 x
screws and three shoulder washers
as shown in Figure C.

5. Replace the stock speaker panels.

5

Mounting the Woofer/Midrange in
Custom Locations

2. Cut out the speaker hole at the
mounting location and drill the three
marked holes with a

1

/8" (3mm) drill.

3. Run speaker wire to the hole location,
making sure that either an active or
the included passive crossover is
connected to the speaker (see Figure K
for wiring details).

1

/4"

4. Put the speaker Fabric Displacement
Ring under the speaker as shown in
Figure D.

1

/4"

Figure D

5. Attach the foam gasket to the back of the
woofer/midrange. Connect the speaker
wire from the crossover terminals marked
“ W” to the speaker by either soldering
(preferred) or using crimp terminals.

1. Snap the grille assembly of the speaker
onto the driver and choose three hole
locations so that the grille logo is oriented
as desired for your installation. Use the
Fabric Displacement Ring included in the
package to mark the location of the three
screw holes and the speaker cutout
holes (cutout hole sizes are listed in the

/8"

Specifications section). Before cutting or
drilling make sure that there are no car
components, electrical wiring or any
other items that could be damaged.

Connect the wire from the “W+” terminal
on the crossover to the red “W” terminal
on the woofer/ midrange. Repeat the
same process for the “W–” terminal (see
Figure K for details).

6. Mount the speaker to the hole location

1

using three #8 x 1

/4" screws and three

shoulder washers as shown in Figure D.

7. Push the grille down onto the speaker
making sure the tabs on the speaker
match with the slots in the grille. Twist

1

the grille about

/2" (12mm) clockwise to

lock the grille into place.

7

A

C

B

GRILLE
FRAME

METAL
GRILLE

Figure E

Note: The metal grille is designed so
that it can be covered with grille cloth if
desired. Simply, remove the metal grille
from the grille frame as shown in Figure E.
Then use spray adhesive to glue and wrap
the grille cloth to the metal grille. Push the
metal grille with cloth back in the grille
frame. For even better interior matching it
is also possible to use plastic compatible
paint to match the grille frame to the
vehicle’s interior.

8

Logo Orientation on Grille

The orientation of the logo on the
metal grille relative to the grille frame can
be adjusted. Simply remove the metal
grille and reassemble the metal grille to
the grille frame utilizing a different tab slot.

Mounting the
408 and 508GTi Tweeter

The 408 and 508GTi Tweeter includes
accessories for four different mounting
configurations. Take a look at all the
possibilities described in the following
paragraphs, pick one, follow the steps and
you’ll soon be done!

Tweeter Surface Mounting
Instructions

a) Using the Mounting Plate Template at
the back of this manual. Pick a mounting
location for the tweeter making sure that
speaker wire can be run to this location.
Flat surfaces work best. Drill the holes as
shown on the template in the desired
mounting location. Use three

3

⁄4"

TWEETER SURFACE MOUNT INSTALLATION

mounting screws to secure the mounting
plate in place as shown in Figure F.

b) Run wire from the 408 and 508GTi
Crossover to the wire feed-through hole
and connect the wire to the tweeter
making sure to connect + to + and – to –
by either soldering (preferred) or using
crimp-on connectors.

c) Push the tweeter down onto the
mounting plate making sure to line up the
bayonet tabs with the slots in the tweeter
housing.

d) Twist the tweeter clockwise about

1

⁄4" to

lock it into position.

Figure F

Tweeter Surface Angle Mounting

A

B

D

C

Instructions

a) Using the Surface Angle Mount
Template at the back of the manual, drill
two screw holes at the desired mounting
location, making sure to choose the
correct tweeter orientation. Secure the
Surface Angle Mount Adapter with two
sheet metal screws as shown in Figure G.

b) Secure the mounting plate to surface
angle mount adapter using two

3

5

⁄16" screws.

⁄4"

c) Run the speaker wire from the 408 and
508GTi Crossover to the wire through hole
and connect the wire to the tweeter
making sure to connect + to + and – to –
by either soldering (preferred) or using
crimp-on connectors.

d) Push the tweeter down onto the
mounting plate making sure to line up the
bayonet tabs with the slots in the tweeter
housing.

e) Twist the tweeter clockwise about

1

⁄4" to

lock it into position.

Figure G

TWEETER SURFACE ANGLE INSTALLATION

9

Tweeter Flush Mounting

C

A

B

D

F

E

Instructions

a) Use a hole saw or other tool and the
Flush Mount Template at the back of this
manual to make a hole for the flush mount
cup in the desired location. Secure the
metal spring to the Flush Mount Cup
using one metal spring screw as shown
in Figure H. Tighten the screw only enough
to keep the metal spring from falling off.

b) Push the Flush Mount Cup with the
metal spring into the hole that was cut in
step a.

Flush Mount Cup

c) Tighten the larger

3

⁄4" spring mounting
screw to lock the Flush Mounting Cup into
the mounting hole.

d) Secure the mounting plate to the Flush
Mount Cup using three

5

⁄16" screws.
Connect the speaker wire from the
crossover to the tweeter (see Figures I
and K), making sure to observe correct
polarity.

e) Push the tweeter down onto the
mounting plate making sure to line up the
bayonet tabs with the slots in the tweeter
housing.

f) Twist the tweeter clockwise about

1

⁄4" to

lock it into position.

Figure I

TWEETER FLUSH MOUNT

INSTALLATION

FLUSH MOUNT INSTALLATION

10

Figure H

Tweeter Flush Angle Mounting

E

D

Instructions

a) Follow steps a through c in the Tweeter
Flush Mounting Instructions.

b) Secure the Flush Angle Mount Adapter
to the Flush Mount Cup using two
screws as shown in Figure J.

c) Connect the 408 and 508GTi speaker
wires (from the crossover) to the tweeter,
observing correct polarity (see figure K for
details).

d) Press the tweeter down onto the Flush
Angle Mount Adapter lower portion, making
sure to line up the snaps with the slots in
the tweeter housing.

e) Snap the other portion of the tweeter
down onto the angle adapter.

5

⁄16"

Figure J

TWEETER FLUSH ANGLE

INSTALLATION

11

Wiring

LIFT

PRESS

508 GTI Crossover

INPUTWOOFERTWEETER

INPUTWOOFERTWEETER

BLACK

(–)

RED

(+)

Connect to

White “W”

Terminal

Connect to

Red “W”
Terminal

Use 2-conductor stranded type,
insulated wire to connect the 408 and
508GTi Woofer/Midrange and tweeter to
the included crossover, and the crossover
to the amplifier as shown in Figure K.

A minimum wire gauge of 18AWG is
recommended, with larger size suggested
for wire runs longer than 10 feet.

Figure K

12

The polarity (the positive / negative
orientation of the connections) for every
speaker and crossover to amplifier
connection must be consistent from left to
right channel to assure proper imaging and
optimum frequency response. This does not
mean that the woofer/midrange should
always be connected in the same polarity
as the tweeter however. It is possible, that
due to the difference in the distance the
sound travels from the woofer/midrange to
your ears compared to the distance from the
tweeters in a typical system, and the short
wavelengths of sound at the crossover
frequency, that a connection where the
tweeters are connected in reverse polarity
from the woofer/midrange drivers may
actually result in better sound. Because
there is no way to accurately predict this
before installation, we recommend that you
try the connection both ways, and leave it in
the polarity that gives the smoothest audible
transition between the woofer/midrange and
tweeter. When the tweeter and woofer/
midrange drivers are mounted close to
each other, the in-phase connection will
usually yield the best sound.

Crossover Tweeter Level
Adjustment

The Gti System Crossover allows you
to adjust the level of the GTi Systems
Tweeter. This adjustment is located under
the crossover cover. To remove this cover
simply press on the end of the cover
(as shown in Figure L) and lift off. The
adjustment of the tweeter level is done by
setting the switch on the crossover (see
Figure M) to the “0dB,” “–2dB” or “–4dB”
position. Set this switch in the position that
matches your personal preference. Both
crossovers should have this switch set in
the same position.

Figure L

OdB
–2dB
–4dB

Tweeter Level Adjustment Switch

Figure M

System Connections

There are a variety of system options
available with the 408 and 508GTi. The
simplest configuration is to use the 408
and 508GTi full range. Although this will
yield good sound, the best performance
will be achieved in a high-end system
which includes subwoofers and, optionally,
midbass transducers. Because the 408
and 508GTi are specifically designed
for mid and high frequency operation,
they should have their extremely low
frequencies blocked by electrical means in
order to achieve the best system fidelity
and the widest dynamic range. Full range

use may be obtained at slightly lower
power handling levels.

For the best performance, we
recommend that an active crossover with
a minimum of 12dB per octave slope be
used for the transition point between the
Subwoofer and the 408 or 508GTi. The
optimum crossover frequency for this
transition is dependent on the specific
components used, the vehicle, and other
installation details. As a general rule, the
crossover frequency should be as low as
possible to achieve the best system
imaging. You can fine-tune the crossover
after the installation is complete for the
best sound. Agood place to start your
tuning process is between 60Hz and
150Hz when using the 508GTi and
between 80Hz and 150Hz when using the
408GTi. In 4-way systems using a midbass
driver such as the 600GTi, the crossover
point may be raised higher without
detrimentally affecting imaging as long
as the woofer/midbass drivers can
be mounted reasonably close to the
woofer/midranges. This higher crossover
frequency will allow the system to play

louder. Since no crossover is perfect, it is
advisable to keep your crossover points
away from the range where your hearing is
most sensitive. Therefore we recommend
that you try to keep the high-pass
frequency below 250Hz. This lets the 408
or 508GTi reproduce the entire range of
frequencies covering the most important
vocal and lead instrument fundamentals
and their harmonics.

If you prefer to use all passive
crossovers, you will need to construct
or purchase a high-pass filter for the
subwoofer to woofer/midrange transition
point and install it in-line ahead of the 408
or 508GTi Crossover. For the best system
dynamic range, we recommend that a
minimum slope of 12dB per octave be
used.

The most advanced system designs
use active electronic crossovers such as
the JBL GTX2, GTX4 or GTX47 at both
the subwoofer (or woofer/midbass)-to­woofer/midrange transition point and at the
woofer/midrange-to-tweeter transition. Set
the high crossover frequency at or above
5kHz if a 12dB per octave crossover is

13

used and at or above 3.5kHz if you are
using an 18 or 24dB per octave crossover.
In this configuration, the crossovers
supplied with the 408 and 508GTi are
not used. For tweeter protection, a 1.5A
fast acting fuse should be installed in
series with the tweeter. The maximum
recommended RMS amplifier power
routed directly to the woofer/midrange is
150 watts for the 408GTi and 200 watts for
the 508GTi. The maximum recommended
RMS amplifier power routed directly to the
tweeter is 125 watts.

Speaker Break-In

The 408 and 508GTi Woofer/
Midranges use many high strength
materials which require a break-in period
before they will achieve top performance.
The drivers need to be broken in at a
medium volume level for about 1 hour
before maximum performance is achieved.

A Note on Power Handling

As a result of their high efficiency , all

14

JBL loudspeakers will produce reasonable
volume levels in the automotive environment
using very little amplifier power. However,
the use of a low-powered amplifier to attain
very high volume levels could lead to
overdriving the amplifier. This will generate
high distortion levels which can easily
damage loudspeakers,

even if the rated
power of the amplifier is below the rated
maximum power handling of the
loudspeaker!

As a general rule, do not turn up the
volume control past the point where you
hear distortion in the form of either signal
distortion from an overdriven amplifier or
mechanical noise from an overstressed
speaker.

For the best performance and
system reliability, you should select an
amplifier with an output rating greater than
the maximum power likely to be used to
generate the desired volume levels.

want your system “Loud + Clear,” we
suggest that you step up to a JBL power
amplifier which has an RMS power rating
equal to, but not exceeding, the

Recommended Amplifier Power

the specifications of your specific JBL

If you

Maximum

listed in

speaker. This margin of reserve power will
ensure that the amplifier will not attempt to
deliver more power than its design allows.
Your dealer will be happy to point out
which high power JBL amplifiers are
optimum for your application and listening
habits.

Following these guidelines will provide
virtually distortion free sound reproduction
and long loudspeaker life.

In Case of Difficulty

The most common difficulties are
noise, distortion, and intermittent
connections.

System noise is usually not the fault
of the 408 and 508GTi. Hiss or “alternator
whine” is most often the result of faulty
grounding of the system electronics or
improper setting of amplifier level controls.
An exception to this is if the passive
crossover networks are mounted near a
source of radiated noise, the network may
pick up this noise with sufficient power to
drive the 408 and 508GTi. For this reason,
be careful not to mount any passive

crossovers near wires carrying high
currents such as battery cables or wires
leading to ammeters or tachometers.

Distortion is usually the result of
overdriving one or more components in
the system. The problem is most likely
insufficient amplifier power, or improper
setting of gain controls. Refer to the
instructions which came with the
electronics for assistance. The 408 and
508GTi will not play as loudly, or handle
the full rated power, when used without a
subwoofer and associated high-pass
crossover. When using the 408 or
508GTi full-range, be careful to limit the
volume level to that which can be
reproduced without audible distortion
from the speaker.

If you want to talk to us about any
problems, call JBL Customer Service at
1-800-336-4JBL (4525) between 9AM
and 5PM eastern time.

15

Specifications: 408GTi 508GTi
Frequency response: 80–22kHz 60–22kHz
Recommended minimum High-Pass Crossover

Frequency for Medium Power Operation: 80Hz 60Hz
Continuous Power Handling With 12dB

Passive Network High Passed at
Recommended Minimum Frequency: 100 Watts 150 Watts

Continuous Power Handling with 12dB Passive
Network High Passed at 150–200Hz
(Midrange Operation): 150 Watts 200 Watts

Continuous Power Handling When Used
Without High-Pass (Full-Range Operation): 75 Watts 100 Watts

Minimum Recommended Amplifier Power: 20 Watts 20 Watts
Maximum Recommended Amplifier Power Rating: 150 Watts 200 Watts
Sensitivity (2.83 Volts / 1 Meter): 89dB 91dB
Impedance 4 Ohms 4 Ohms
Dimensions – Woofer/Midrange Transducers
Overall Maximum Diameter

3

(Mounting Tab to Frame Edge): 4
Height: 2
Mounting Depth: 1
Cutout Size: 3
Dimensions – Tweeter
Overall Diameter: 1
Height:
Height With Angle Adapter: 1
Flush Mount Cutout Diameter: 2
Flush Mount Depth:
Dimensions – Crossover Network (LxWxH): 5

/8" (111mm) 51⁄8" (130mm)

1

⁄8" (54mm) 23⁄8" (60mm)

7

⁄8" (48mm) 21⁄16" (53mm)

3

⁄4" (95mm) 43⁄4" (121mm)

15

⁄16" (50mm) 115⁄16" (50mm)

11

⁄16" (18mm)

1

⁄2" (38mm) 11⁄2" (38mm)

1

⁄8" (54mm) 21⁄8" (54mm)

15

⁄16" (23mm)

10

/16" x 33/16" x19/16"5

11

⁄16" (18mm)

15

⁄16" (23mm)

10

/16" x 33/16" x 19/16"

(143mm x 81mm x 40mm) (143mm x 81mm x 40mm)
Woofer/Midrange Weight: 1 lb. 7 oz. (0.66kg) 1 lb. 10 oz. (0.75kg)
Tweeter Weight: 2.5 oz. (71 grams) 2.5 oz. (71 grams)

16

Thiele-Small Specifications: 408 GTi 508 GTi
Free Air Resonance (Fs): 125Hz 100Hz
Electrical Damping (Qes): 0.52 0.51
Mechanical Damping (Qms): 5.17 5.14
Total Damping (Qt): 0.47 0.4
Equivalent Volume of Compilance (Vas): 0.0388 cu. ft. (1.10 liters) 0.1059 cu. ft. (3.0 liters)

2

Effective Cone Area (Sd): 9.3 sq. inches (0.0060 m

) 14.26 sq. inches (0.0092 m2)
Center to Peak Linear Excursion (Xmax): 0.126 inches (3.2mm) 0.126 inches (3.2mm)
Voice Coil DC Resistance (Re): 3.4 ohms 3.4 ohms
Voice Coil Inductance (Le): 0.22mH @ 1kHz 0.22mH @ 1kHz
Voice Coil Diameter: 2 inches (51mm) 2 inches (51mm)
Voice Coil Length (Winding Length): 0.400 inches (10.2mm) 0.400 inches (10.2mm)
Air Gap Height: 0.200 inches (5.1mm) 0.200 inches (5.1mm)
BL Product: 6.2 T/M 6.2 T/M
Effective Moving Mass (Mm): 0.28 oz. (8.0 grams) 0.32 oz. (9.0 grams)
Note: The Thiele-Small specifications shown apply only after a break-in period of approximately 2 hours.
JBL continually strives to impove its products. New materials, production methods and other refinements may result in a change from published

specifications and description. The changes will equal or exceed the original specifications, unless otherwise stated.

17

Tweeter is angled
in this direction

Drill

3

/32" (2.9mm)

hole in two places

Drill 11/32" (8.7mm)
holes for wire feed through

TWEETER
SURFACE
ANGLE
MOUNT
TEMPLATE

19

Drill 3/32" (2.4mm)
holes for
mounting screw

Drill

11

/32" (8.7mm)
holes for
wire feed through

TWEETER
MOUNTING
PLATE
TEMPLATE

21

Cut Hole Using
2

1

/8-21/4" (54mm)

hole saw

TWEETER FLUSH
MOUNT TEMPLATE

23

JBL Consumer Products, Inc.
80 Crossways Park West
Woodbury, NY 11797
8500 Balboa Blvd.
Northridge, CA 91329
1-800-336-4JBL

A Harman International Company

NMGP/N:306385-001 5/94