Alpine 3681 Manual De Instalación Y Operación página 20

ADJUSTMENT USING AN RTA:
1. Turn the sound system on, verify that all compo-
nents are functional, and place all controls such as
Bass, Treble, Fader, Balance, in-dash equalizer con-
trols (if any) are in the center (neutral) position. Al-
so verify that the Subwoofer Fading Mode Switch,
Subwoofer Stereo/Mono Switch, and Front and
Rear Crossover Mode are set as needed.
2. Using atestCD or tape such as the Alpine Official
Reference Software, select the "Pink Noise" track
and set the volume control of the system for anom-
inal 100 dB average sound pressure level.
Perform the following steps with all doors
closed, windows rolled up, and the vehicle inte-
rior completely intact:
3. This sound level will give you a display on the
RTA screen. This display is the frequency response
of the total system (the sound system and the vehi-
cle's interior together). It may look somewhat simi-
lar to the one shown below:
20Hz 200Hz 2kHz
This display shows how many decibels of sound
pressure exist at each frequency. A pleasant
sounding system should have a smooth frequency
response transition. Also, the relative balance be-
tween the different drivers' output levels must be
correct.
Due to different component speaker efficiencies,
power amplifier sensitivity, vehicle interior reson-
ances, speaker and speaker enclosure non-linearit-
ies or interior audio section frequency response, an
unadjusted system may have many peaks and dips
in its frequency response.
The 3681 can be adjusted to balance the acoustical
response and reduce other non-linearities.
Certain frequency regions can also be boosted or
cut to overcome road noise or to accommodate lis-
tener preferences.
4. If you are using a head unit with separate front
and rear pre-outs, verify that the 2-input mode is se-
lected, and fade to the front. Make sure that the
rear drivers are defeated. Remember to keep the
vehicle doors and windows closed during adjust-
ments.
5. Analyze the spectrum display on the RTA to de-
tect any imbalances between the output levels of
each component driver. For example, in the display
shown, the Subwoofer's response is lower than the
mid-bass driver and the mid-bass driver's response
is lower than the midrange speaker.
6. Find out which speaker's output is the lowest
compared to the other bands. This will be the Ref-
erence for all other bands.
In the example shown above, the SUBWOOFER
output is the lowest. Therefore, the MID-BASS,
MID-RANGE and TWEETER outputs must all be cut
in varied amounts for proper adjustment.
7, While observing the RTA screen, adjust the out-
put level control to properly shape and smooth out
the level differences.
8. Adjust and fine-tune the crossover points for
each region to further smooth out the acoustical re-
sponse.
9. If your head unit has a single pre-amp output on-
ly, skip to item 12.
10. Fade to the rear, check for defeated front
speakers, close all vehicle doors and windows, and
repeat steps 5 through 8.