Meyer Sound 750-LFC, Operating Instructions Manual

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CHAPTER 3: AMPLIFICATION AND AUDIO
21
In contrast, TruPower limiting calculates varying loudspeaker
impedances by measuring both current and voltage to
compute the actual power dissipation in the voice coil. This
approach improves performance, both before and during
limiting, by allowing the driver to produce the maximum SPL
across its entire frequency range, while also retaining signal
peaks. TruPower limiting also eliminates power compression
at high levels over lengthy periods, which helps regulate voice
coil temperatures, thereby extending the life of the driver.
LF Limit LED
The 750
-
LFC low-frequency driver is powered by two amplifier
channels, one for each voice coil, which are routed to a single
limiter. When a safe power level is exceeded in either channel,
limiting is engaged for both channels and the LF
Limit LED
(Figure 15) lights on the user panel (the HF Limit LED is
disabled for the 750
-
LFC).
When engaged, the limiter not only protects the driver but also
prevents signal peaks from causing excessive distortion in the
amplifier channels, thereby preserving headroom and
maintaining smooth frequency response at high levels. When
levels return to normal—below the limiter threshold—limiting
ceases.
The 750
-
LFC loudspeaker performs within its acoustical
specifications at normal temperatures when the LF Limit LED
is unlit, or when the LED is lit for 2 seconds or less and then
turns off for at least 1 second. If the LED remains lit for longer
than 3 seconds, the loudspeaker enters hard limiting where:
•
Increases to the input level have no effect
•
Distortion increases due to clipping
•
Drivers are subjected to excessive heat and excursion,
thereby compromising their lifespan
CAUTION: The Limit LED indicates when a safe,
optimum level is exceeded. If a 750
-
LFC
loudspeaker system begins to limit before
reaching the desired SPL, consider adding more units
to the system.
AMPLIFIER COOLING SYSTEM
The 750
-
LFC loudspeaker employs natural convection in its
cooling system. The amplifier’s heat sink provides natural
convection cooling from the air flowing near its fins. When
exposed to high ambient temperatures or when driven
continuously at high output levels, an ultra low-noise, variable-
speed fan circulates air internally to keep the 750
-
LFC cabinet
at a safe operating temperature.
CAUTION: To prevent the 750
-
LFC unit from
overheating, allow at least 6 inches behind the
loudspeaker for proper ventilation. During
extreme operation, the 750
-
LFC loudspeaker’s heat
sink can reach temperatures up to 80° C (176° F). Wait
15 minutes for the unit to cool before touching.
ON/STATUS LED
During normal operation, when the 750
-
LFC is powered on,
the On/Status LED is solid green. If the loudspeaker
encounters a hardware fault, or the unit begins to overheat,
the LED flashes red. In some instances, the loudspeaker will
continue to output audio while the LED flashes red, though
with a reduction in the limiter thresholds (and gain) to protect
the loudspeaker.
If a loudspeaker is overheating (for RMS-equipped
loudspeakers, you can verify this situation in Compass RMS),
a reduction in SPL may be necessary. If, after a reduction in
SPL and an appropriate cooling period the
On/Status LED
continues to flash red (does not return to solid green), contact
Meyer Sound Technical Support.
If the On/Status LED flashes red and the loudspeaker does
not output audio, contact Meyer Sound Technical Support
immediately.
CAUTION: If a 750
-
LFC loudspeaker system
consistently overheats before reaching the
desired SPL, consider adding more units to the
system.
NOTE: During startup, the On/Status LED
flashes multiple colors successively. For more
information about the power on sequence, see
“Intelligent AC Power Supply” on page 16.
TIP: When the 750
-
LFC loudspeaker is connected
to an RMS network, the Compass RMS software
provides additional feedback on the loudspeaker’s
hardware status and operating temperature. For more
information, see Chapter 5, “RMS Remote Monitoring
System.”
Figure 15: 750
-
LFC Limit LEDs (HF LED Disabled)
!
!
!
LF Limit LED