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4. CABLE ROUTING AND WIRING
4.1 POWER WIRES
Attach the ground cable to the GND terminal on the backside of the active subwoofer. In
most cases it will be best to keep the ground cable („-12V“) as short as possible, i.e. to
find a chassis contact very close to the active sub. The ground power wire must have the
same cross-section as the positive power cable. The contact point where the ground wire is
attached to, must be solid and clean, i.e. free from rust or paint!
4.2 RCA & REMOTE WIRES
Carefully run the RCA interconnect and the amp-remote wire from your headunit to the
respective inputs on your active sub. The audio signal cables should always be routed
completely separate from the power cables.
5. CROSSOVER ADJUSTMENTS
5.1 LOWPASS X-OVER FREQUENCY
The lowpass cut-off frequency setting, marked as „CROSSOVER“ on the amp-module,
depends on some variables, i.e. the bass response of the loudspeakers installed in the car.
As a rule of thumb, settings in a range between 80 to 100 Hz will render best sonic results.
For an intermediate lowpass crossover setting to attempt input gain and phase-shift control
adjustments, go for a VR-pot set to approx. 80 Hz – and after input gain and phase have
been adjusted, it is advisable to fine tune the lowpass crossover frequency for best possible
sound quality.
Note: In general, setting the lowpass crossover frequency too low, will result in a weak
and muddy sounding bass, while setting this crossover frequency too high will result in a
‘booming’ bass sound and reduced low end extension.
5.2 INPUT LEVEL ADJUSTMENT
To reach a maximum in dynamic response from each individual head-unit/amplifier/speaker
combination, it is important to set the respective input level controls („GAIN“) of the amp-
module correctly.
Before you start, you MUST set all tone controls (Bass, Mid, Treble, Loudness etc.) and the
fader on the head unit to their neutral or center positions.
Switch on your headunit, and set the playback level to a medium volume.
Now turn up the input “GAIN” control of the active subwoofer, until you hear enough bass
volume. Close the trunk of your car, listen to the result and fine tune the GAIN level by turning
the pot down or up, until a good tonal overall balance with enough bass is achieved.
5.3 PHASE-SHIFT ADJUSTMENT
The phase shift function of the AB25A can not be deactivated, it is permanently in the signal
chain. The phase-shift control enables you to match the acoustical phase relations of the
active subwoofer and the speaker system of your car. A good match of the acoustical phase
between subwoofer and the system in the front doors will give you the impression of bass
coming from a place in front of you. This setting must be played entirely by ear.
