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BassPro II is equipped with two line-
level (RCA) inputs and two high-level
inputs. To help you plan the installation
of BassPro II, we have included two 
system application diagrams in
Figures 8 and 9. For more installation
suggestions, contact your local 
authorized JBL car audio dealer.

Splices

(not supplied)

Splices

(not supplied)

Figure 9. Line-level connections 
with two outputs (single full-range 
or subwoofer).

Figure 8. High-level connections.
Connect BassPro II’s high-level
inputs to either the front or rear
speaker outputs of your head unit
(splice crimps not included).

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BassPro II has controls and indicators
that help simplify sonic integration with
almost any vehicle’s unique acoustic
properties. These controls are located
on the amplifier panel, as shown in
Figure 10.

Power LED
Gain Control
Crossover
Remote Bass Control
Auto Turn-On 

POWER LED: This indicator 
will glow red when the BassPro II 
is operating.

GAIN CONTROL: Use this 
control to adjust the relative volume
(loudness) of BassPro II with the other
speakers in the vehicle.

CROSSOVER: Use this control 
to adjust the amount of high-frequency
information present in BassPro II’s out-
put. A lower value signifies less high-
frequency content.

3. Turn the head unit ON and play a

selection of your favorite music
track that has substantial bass. 

4. Adjust the CROSSOVER control

counterclockwise, until you hear
only low-frequency information. 
Example – you should not hear
vocals coming from BassPro II 
when seated in the normal listening 
position.

5. Adjust the BASS CONTROL either

clockwise or counterclockwise to
suit your taste, and to avoid audible
distortion.

6. If you elect not to install the Remote

Bass Control, adjust the GAIN 
control to the maximum level that
provides undistorted output from 
the BassPro II, with the head unit’s
volume control at its 3 o’clock 
setting.

NOTE: In most cases the above steps
will provide you with satisfactory
results. However, the actual process
may require several readjustments of
each control, since the settings will
interact with one another. If necessary,
consult your authorized JBL car audio
dealer for help in tuning your system.

AUTO TURN-ON: For speaker-
level connections, used this switch to
activate (or deactivate) BassPro II’s
automatic turn-on circuit. For most
speaker-level applications, slide the
switch to the AUTO position. If you 
prefer to use the remote (REM) 
connection, slide the switch to the 
OFF position.

REMOTE BASS
CONTROL: Use this RJ-11 jack 
to connect the supplied remote bass
control.

SETTING THE CONTROLS:
1. Make sure the head unit is off and

VOLUME control is set to minimum.

2. On BassPro II’s amplifier panel, set

the CROSSOVER to its maximum 
frequency of 120Hz, as shown in
Figure 10. 

NOTE: If using the REMOTE BASS
CONTROL, set GAIN to maximum 
and set the BASS CONTROL to the 
midpoint.

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POWER LED is not lit. 

1. Fuse is blown and needs 
replacement.
2. Head unit not functioning properly. 
3. Check remote turn-on, power and 
ground connections.  

POWER LED is lit but there is no bass. 

1. Inputs are not connected. Check 
connections.
2. Head-unit fader controls are not set 
properly. Adjust head-unit controls to 
feed audio signals to BassPro II.  
3. Incorrect GAIN control setting.

Output sounds muddy or distorted. 

1. GAIN is set too high. 
2. Bass level is set too high on 
head unit.
3. Head unit output is distorted or 
blown. See your authorized JBL car 
audio dealer.  

Output gets louder when the head-unit 

Using speaker-level connection: one of 

balance is adjusted to L or R. 

the speaker connections is reversed 
(+/–). Reverse one channel.   

POWER LED remains ON after system 

Speaker-level connections have a five-

is turned off.  

minute turn-off delay. Check the unit at 
a later time.  

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The Subwoofer Level Control may be
mounted under the dash or dismantled
and mounted in the dash for a factory-
installed appearance.

UNDER-DASH MOUNTING 
Select a mounting location that allows
easy access to the control while driv-
ing. Using the Subwoofer Level Control
as a template, mark and drill holes in
the mounting surface. Attach the
Subwoofer Level Control using the
mounting screws provided (Figure 4). 

IN-DASH MOUNTING
Disassemble the Subwoofer Level
Control by removing the two Phillips-
head screws on the front panel, 
rear panel and on top. Remove the
Subwoofer Level Control’s bottom and
side panels. Slide the Subwoofer Level
Control’s PC board forward to release
the RJ11 connector from the back
panel and remove the board along with
the potentiometer, knob and connector
as a single assembly.   

Choose a mounting location that
allows easy access to the control, 
and provides 1-3/4" clearance behind
the mounting surface. Drill a 9/32" 
hole in the mounting surface. Feed 
the Subwoofer Level Control’s 
potentiometer shaft (with the knob
removed) through the hole and use the
nut and washer provided to hold the
control in place (Figure 5). 

Route the cable behind the dash or
other interior panels and under the
carpet. Do not route the cable outside
the vehicle. Connect the RJ11 cable
between the RJ11 receptacle on the
BassPro II and the receptacle on the
Subwoofer Level Control (Figure 6). 

Figure 4. Under-dash mounting of the
Subwoofer Level Control. 

Figure 5. In-dash mounting of the Subwoofer Level Control.

Figure 6. Subwoofer Level Control electrical
connection.

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