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MM-10 OPERATING INSTRUCTIONS
31
CAUTION: If the Limit LED turns red and stays
solid red after powering up and the audio is
muted, the subwoofer has encountered a failure and
may need to be serviced. Contact Meyer Sound
Technical Support.
CAUTION: If the Limit LED turns solid red and
the MM-10ACX continues to output audio,
though at reduced levels, the subwoofer’s voltage
may have dropped below 90 V AC. When these con-
ditions are encountered, operation of the subwoofer
should cease and its power supply and cabling
should be verified.
Limiting (Yellow)
Limiting activity is indicated when the Limit LED turns yel-
low. When engaged, the limiter protects the subwoofer’s
driver and prevents signal peaks from causing excessive
distortion in the subwoofer’s amplifier, thereby preserving
headroom and maintaining smooth frequency responses at
high levels. When the level returns to normal, below the lim-
iter’s threshold, the LED turns green and limiting ceases.
The MM-10ACX performs within its acoustical specifications
at normal temperatures when the Limit LED is green, or if the
LED turns yellow for two seconds or less and then returns to
green for at least one second. If the LED remains yellow for
longer than three seconds, the subwoofer enters hard limit-
ing where:
■ Increases to the input level have no effect.
■ Distortion increases due to clipping and nonlinear driver
operation.
■ The drivers are subjected to excessive heat and excur-
sion, which will compromise their life span and may
eventually lead to damage over time.
CAUTION: The Limit LED turns yellow when
the subwoofer’s signal rises 2 dB above the
limiting threshold, and indicates a safe, optimum level
has been exceeded. If the MM-10ACX subwoofers in
a system begin to limit before reaching the desired
SPL, consider adding more subwoofers to the sys-
tem to achieve the desired SPL without exposing the
subwoofers to excessive levels and possible over-
heating.
MM-10ACX Temperature and Limiting
The Limit LED turns solid yellow when its heat sink tempera-
ture reaches 65° C (145° F), indicating the unit is reaching its
maximum heat dissipation and a reduction in SPL is recom-
mended. While the MM-10ACX will continue to operate
while the LED is yellow, the limiter threshold is lowered to a
safe level (causing the output level to be lowered by 6 dB) to
prevent the subwoofer from overheating. When the temper-
ature of the heat sink cools to 50°C (122°F), the LED
changes from yellow to green and the limiter threshold
returns to normal.
Clipping (Red)
The Limit LED flashes red when its input signal causes the
amplifier to overload. If the LED flashes red continuously, the
subwoofer is severely overloaded and a reduction in the
input level is recommended.
CAUTION: If the Limit LED turns solid red and
the subwoofer continues to output audio,
though at reduced levels, the subwoofer’s voltage
may have dropped below 90 V AC. When these con-
ditions are encountered, operation of the subwoofer
should cease and its power supply and cabling
should be verified.
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