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17
Calibration
Calibration must be performed when the ambient noise in the loudspeaker coverage area is at its
normal minimum level for the area. (NOT dead quiet, unless that is normal.)
1.
Complete all input and output connections. There must be program audio present at a
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INE
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connection before calibration can be completed. If the system is used for
paging, activate the paging system by having an assistant count or recite the alphabet
during the entire calibration procedure. The audio input level must be greater than -35 dBu
or the 572 will not recognize the presence of audio and the M
USIC
/P
AGE
E
RROR
light will
flash.
2.
Warn any people present that sound system may get momentarily loud.
3.
Set the front panel controls as described in Calibration Settings Table (previous page).
4.
Verify that program audio is audible in the system speakers.
5.
Set the system power amplifier’s volume control to a comfortably loud level. Do not
readjust this control after calibration of the 572 or your calibration will be invalid.
6.
Set the B
YPASS
switch to the OUT position.
7.
Use a pencil to push the C
ALIBRATE
button in and then release it.
8.
The red MIN lamp lights. Adjust the M
IN
C
ALIBRATE
knob to a comfortable listening level.
The system audio level will stay at this level for 10 seconds. This level is the minimum
level that the 572 allows in the space, regardless of how quiet the ambient noise level may
be or get.
9.
When the red MAX lamp lights adjust the M
AX
C
ALIBRATE
knob to set the system level to
as loud as you ever want the volume to go during noisy times. Check that the power
amplifier(s) aren’t clipping. The system audio level will return to normal in 10 seconds. It
may be helpful to monitor the acoustical level in the space with a sound level meter.
10.
Calibration is complete. The 572 will adjust the system level as the ambient noise in the
area increases.
Quick System Test
•
While talking loudly or making noise near a system speaker turn the S
AMPLE
I
NTERVAL
control to “1” and then quickly return it to “5”. This forces the system to sense. The
system level should increase in response to the increase in ambient noise.
•
While remaining quiet, turn the S
AMPLE
I
NTERVAL
control to “1” and then quickly return it
to “5”. This forces another sense. The system level should return to the minimum level.
Options, Options and More Options
The option switches allow tailoring the 572 to different installation scenarios. There are four option
switches.
Option A sets the music silence threshold. This threshold is the signal level at the M
USIC
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INE
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that the 572 considers silent. Signals below this threshold are considered silent, and are fair
game for sense intervals. In installations where the ambient noise level is fairly low, and where the
background music has a great deal of dynamic range (like classical music from a CD player), you
may need to keep the signal level through the 572 quite high, as well as using the lower silence
threshold, and reducing the gain at the power amplifier input to put the music back to a comfortable
level. This prevents the 572 from punching holes in the program material during quiet passages.
Option B forces the 572 to sense mode and displays the output of the sense preamplifier on the
front-panel bargraph. Use option B to view the signal level returned from the loudspeakers in sense
mode and to verify that the signal level falls within the 572’s limits for proper operation. The ideal
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