Manual-7
c. Set the reference level for the Low Output:
i) UnMUTE the Low Output.
ii) Adjust the Low Output LEVEL so the RTA LED
associated with the Low / Mid crossover frequency, is
green.
d. Set the Low Output Delay:
i) e Mid Output Delay was previously set and must
not be changed.
ii) UnMUTE the Low and Mid Outputs.
iii) If the level goes down, driver polarity may be wrong.
Check the driver polarity before proceeding.
iv) Adjust the Low Output Delay for maximum
signal level in the RTA band associated with the
Low / Mid crossover frequency.
STEP THREE: Set CD Horn EQs
(if required)
Constant Directivity (CD) Horns need additional equalization to
help cover the same area as a long-throw horn. e
AC 24 has independent CD Horn EQ circuits for Hi-Mid and
High Outputs. It is important to know the 3 dB down point of
the CD Horn driver’s frequency response. e manufacturer of
your driver can supply you with a response curve.
NOTE: If CD Horn EQ is not required, make sure the HORN EQ
filters are OFF and frequency settings are at 8 kHz.
1. Find the frequency where the high end starts to roll off, and
look for the frequency on the chart that has an amplitude 3 dB
down from that point (toward the right, as the higher frequen-
cies roll off).
2. Set the CD Horn EQ frequency to the frequency that cor-
responds to the 3 dB down point indicated on the graph and
engage the filter. (an approximate is fine, it doesn’t have to be
exact)
STEP FOUR: Set Output Levels
1. Set all AC 24 Output LEVEL controls to minimum.
2. MUTE all AC 24 Outputs.
3. Set the INPUT LEVEL controls at unity (white dot between 7
& 8).
4. Realtime Analyzer setup:
a. Place the RTA mic on axis, 1 meter away from
the Low driver as shown in Figure 5, Position-1.
b. Set RTA Scale to 3 dB, if available.
c. Turn on Pink Noise.
5. Set the Low Output Level:
a. UnMUTE the Low Output and slowly turn up the LOW
LEVEL control until you hear a healthy level of noise
through the low frequency drivers (sounds like rumble).
b. Adjust the LOW LEVEL to light the most 0 dB LEDs
in the Low frequency passband.
c. MUTE the Low Output.
6. Set the Mid Output Level:
a. Move the RTA mic to Position 2.
b. Without adjusting the realtime analyzer, UnMUTE the
Mid Output and adjust the MID LEVEL control to light
the most 0 dB LEDs in the Mid output passband.
c. MUTE the Mid Output.
7. Set the Hi-Mid Output Level:
a. Move the RTA mic to Position 3.
b. Without adjusting the realtime analyzer, UnMUTE the
Hi-Mid Output and adjust the HI-MID LEVEL control to
light the most 0 dB LEDs in the Hi-Mid output passband.
c. MUTE the Hi-Mid Output.
8. Set High Output Level:
a. Move the RTA mic to Position 4.
b. Without adjusting the realtime analyzer, UnMUTE the
High Output and adjust the HIGH LEVEL control to light
the most 0 dB LEDs in the High output passband.
c. MUTE the High Output.
1
Note: Contrary to popular belief, dynamic headroom is optimized by setting amplifier sensitivity so that the amplifier clips at the same point
the signal processing clips (typically +20 dBu to +24 dBu). For example, if the noise floor is –80 dBu and the maximum signal level is +20
dBu, then the dynamic range is 100 dB. If the amplifier is set to clip at +4 dBu, then the dynamic range is 84 dB. Or, 16 dB worse!
(13 pages)
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