4
Tuning - Control and Functions - Adjustment
J B L BASSTU B E BTX250
TUNING BTX250
BTX250 provides several controls that
simplify sonic integration with virtually
any vehicle’s unique acoustic proper-
ties. Please read the following section
carefully to familiarize yourself with the
function of each control.
Figure 6.
Locations of controls.
Phase Control:
The phase control is a
switch located on the panel with the
electrical connections (see Fig. 6). This
switch will reverse the phase of
BTX250’s output with respect to its
input. When installing BTX250 with an
existing factory or aftermarket system,
depending on BTX250’s location in the
vehicle and the distance between it
and the other speakers in the car,
reversing the phase (by moving the
phase switch) may produce a discern-
able increase or decrease in the
amount of upper bass reproduced.
Although the position that yields the
most upper bass is technically correct,
you may choose the position that
better suits your taste.
CONTROLS and FUNCTIONS
Gain Control:
This control will adjust
the input sensitivity of BTX250. Use
this control to adjust the relative
volume (loudness) of BTX250 with
respect to the other speakers in the
vehicle.
Crossover:
The crossover control
adjusts the amount of high-frequency
information present in BTX250’s
output.
Bass Boost:
BTX250’s interaction
with the acoustics of your vehicle may
produce a peak or dip in BTX250’s
response. For the vast majority of
vehicles, these peaks or dips occur at
about 40-50Hz — around the frequen-
cy of a low bass guitar note. Use this
control to correct that peak or dip.
Adjustment between 0dB and +6dB is
possible. Although response without
any sharp peaks or dips is technically
correct, you may choose the position
that best suits your taste.
Power LED:
The power LED will glow
green to indicate that BTX250 is oper-
ational.
ADJUSTMENT SEQUENCE
1. Start with gain control set to mini-
mum and the crossover control and
bass control rotated midway, to 12
o’clock.
2. Choose program material with sub-
stantial bass content and turn the vol-
ume control on your head unit to three-
quarters of its total output (approxi-
mately 3 o’clock on rotary controls).
3. Adjust the gain control clockwise
until you start to hear some distortion
coming out from the BTX250.
Then slightly decrease the gain control
counter clockwise.
4. Listen to your system, making a
mental note of the amount of upper
bass being reproduced.
5. Switch the phase control to 180°
and listen again for upper bass con-
tent. There may be more upper bass,
less upper bass, or no change at all.
The position that provides the most
upper bass is correct, but choose either
setting according to your taste.
6. Adjust the crossover control clock-
wise or counterclockwise until you hear
only low-frequency information. For
example, you should NOT hear any
vocals coming from BTX250 when
seated in the normal listening position.
7. Adjust the bass-boost control clock-
wise or counterclockwise to suit your
taste.
Note: In most cases, the above steps
will provide satisfactory tuning.
However, the actual process may
require several readjustments of each
control, since the settings will interact
with each other. If necessary, consult
your authorized JBL car audio dealer
for help in tuning your system.
