JBL 408 GTi User Manual / Operation Manual ▷ View online
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
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.
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. A good 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
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. A good 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.
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.
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)-to-
woofer/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
the JBL GTX2, GTX4 or GTX47 at both
the subwoofer (or woofer/midbass)-to-
woofer/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
OdB
–2dB
–4dB
–4dB
Tweeter Level Adjustment Switch
Figure M
408/508 MANUAL.QXP 7/17/98 11:21 AM Page 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.
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.
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
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,
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!
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.
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. If you
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
amplifier with an output rating greater than
the maximum power likely to be used to
generate the desired volume levels. If you
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
Maximum
Recommended Amplifier Power listed in
the specifications of your specific JBL
the specifications of your specific JBL
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.
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.
and long loudspeaker life.
In Case of Difficulty
The most common difficulties are
noise, distortion, and intermittent
connections.
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
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
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408/508 MANUAL.QXP 7/17/98 11:21 AM Page 14
crossovers near wires carrying high
currents such as battery cables or wires
leading to ammeters or tachometers.
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.
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.
1-800-336-4JBL (4525) between 9AM
and 5PM eastern time.
15
408/508 MANUAL.QXP 7/17/98 11:21 AM Page 15
16
Specifications:
408GTi
508GTi
Frequency response:
80 – 22kHz
60 – 22kHz
Recommended minimum High-Pass Crossover
Frequency for Medium Power Operation:
Frequency for Medium Power Operation:
80Hz
60Hz
Continuous Power Handling With 12dB
Passive Network High Passed at
Recommended Minimum Frequency:
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):
Network High Passed at 150–200Hz
(Midrange Operation):
150 Watts
200 Watts
Continuous Power Handling When Used
Without High-Pass (Full-Range Operation):
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
(Mounting Tab to Frame Edge):
4
3
/
8
" (111mm)
5
1
⁄
8
" (130mm)
Height:
2
1
⁄
8
" (54mm)
2
3
⁄
8
" (60mm)
Mounting Depth:
1
7
⁄
8
" (48mm)
2
1
⁄
16
" (53mm)
Cutout Size:
3
3
⁄
4
" (95mm)
4
3
⁄
4
" (121mm)
Dimensions – Tweeter
Overall Diameter:
1
15
⁄
16
" (50mm)
1
15
⁄
16
" (50mm)
Height:
11
⁄
16
" (18mm)
11
⁄
16
" (18mm)
Height With Angle Adapter:
1
1
⁄
2
" (38mm)
1
1
⁄
2
" (38mm)
Flush Mount Cutout Diameter:
2
1
⁄
8
" (54mm)
2
1
⁄
8
" (54mm)
Flush Mount Depth:
15
⁄
16
" (23mm)
15
⁄
16
" (23mm)
Dimensions – Crossover Network (LxWxH):
5
10
/
16
" x 3
3
/
16
" x1
9
/
16
"
5
10
/
16
" x 3
3
/
16
" x 1
9
/
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)
408/508 MANUAL.QXP 7/17/98 11:21 AM Page 16
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