Manual-13
Setting Levels Using an SPL Meter
and Pink Noise Generator
The MUTE switches on the AC 22B make using an SPL
meter an easy and relatively accurate means of tuning a
system. First, obtain a good SPL meter from a local electron-
ics or hi-fi store. Second, and perhaps a little trickier, get a
hold of a pink noise generator—again try electronics and hi-fi
stores. You may also use a sweep or tone generator in place
of a pink noise source. If so, be sure to look at several
different tones within each crossover section to get a good
average of driver response.
1. Run pink noise into the crossover Inputs (through the mixer
or directly, as is convenient).
2. Make sure all crossover LEVEL(s) are turned all the way
down and all amplifier level controls are at least half way
up to start with.
3. Turn the crossover MASTER LEVEL(s) half way up. Place
the SPL meter at least 15 feet from the speaker stack and
about chest high. Once positioned, make sure that the SPL
meter remains in the exact same location for the rest of the
procedure. Minimize all background noise (fans, air
conditioners, traffic, wild animals, etc.) to get accurate
readings. Set the SPL meter to “C-weighting”, “slow” if
those switches are present.
4. Slowly turn the LOW LEVEL up until there is a healthy
rumble coming from the bass speakers (For this example
the 3-Way mode is used—the same procedure applies to all
configurations, starting with the lowest frequency and
ending with the highest). Adjust the SPL meter and/or
LOW LEVEL until you get a 0dB reading on the meter.
After this point do not change the controls on the SPL
meter.
5. While leaving the LOW LEVEL control at the 0 dB
adjustment just obtained, press the LOW MUTE switch on
the crossover so that the pink noise disappears from the
bass speakers (revel in the silence...).
6. Now slowly turn up the MID LEVEL control so that pink
noise is heard from the mid frequency speakers. Without
changing any settings on the SPL meter, adjust the cross-
over MID LEVEL control until you obtain a 0 dB reading
on the SPL meter. Now the low and mid speakers are set at
the same level.
7. Now press the MID MUTE switch on the crossover so that
the pink noise again disappears.
8. Repeat this process for each frequency section of the
crossover, ending with the highest frequency. NOTE: It is
possible that you may turn one of the frequency section
output LEVEL controls all the way up and still not have
enough volume for a 0 dB reading (as determined by
previous section levels). This is probably due to different
sensitivities of amps, speakers and other level controls in
the system. When this happens, re-set the SPL meter so that
it reads 0 dB on this frequency section (you may have to
“down range” the meter and re-adjust the crossover
MASTER LEVEL control). Now go back and re-adjust the
previous crossover LEVEL controls, turning these down to
get a 0 dB reading on the meter.
9. Once the HIGH LEVEL control is set for 0 dB on the
meter, disengage all of the MUTE switches on the cross-
over, and check that noise is emitting from all the speaker
components. The crossover should now be aligned. Make
any overall level adjustments with the MASTER LEVEL
level controls and leave the output LEVEL controls
unchanged.
