JBL 508 GTi User Manual / Operation Manual ▷ View online
Tweeter Flush Mounting
Instructions
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.
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.
metal spring into the hole that was cut in
step a.
c) Tighten the larger
3
⁄
4
" spring mounting
screw to lock the Flush Mounting Cup into
the mounting hole.
the mounting hole.
d) Secure the mounting plate to the Flush
Mount Cup using three
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.
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.
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.
10
C
A
B
Flush Mount Cup
FLUSH MOUNT INSTALLATION
Figure H
D
F
E
Figure I
TWEETER FLUSH MOUNT
INSTALLATION
408/508 MANUAL.QXP 7/17/98 11:21 AM Page 10
Tweeter Flush Angle Mounting
Instructions
Instructions
a) Follow steps a through c in the Tweeter
Flush Mounting Instructions.
Flush Mounting Instructions.
b) Secure the Flush Angle Mount Adapter
to the Flush Mount Cup using two
to the Flush Mount Cup using two
5
⁄
16
"
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).
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.
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.
down onto the angle adapter.
11
Figure J
E
D
TWEETER FLUSH ANGLE
INSTALLATION
408/508 MANUAL.QXP 7/17/98 11:21 AM Page 11
Wiring
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.
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.
for wire runs longer than 10 feet.
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.
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
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.
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.
12
Figure K
LIFT
PRESS
Figure L
508 GTI Crossover
INPUT
WOOFER
TWEETER
INPUT
WOOFER
TWEETER
BLACK
(–)
RED
(+)
Connect to
White “W”
Terminal
Connect to
Red “W”
Terminal
408/508 MANUAL.QXP 7/17/98 11:21 AM Page 12
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
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