11
CHAPTER 3
TruPower limiting also eliminates power compression when
the system is operated at high levels for extended periods,
and extends the driver life cycle by controlling voice coil
temperatures.
The 600-HP’s left and right 15-inch cone drivers are pow-
ered by separate amplifier channels, each with a power
detector but routed to one limiter; the limiter tracks both
channels and uses the higher of the two values to engage.
When the safe continuous power level is exceeded in either
channel, the TruPower limiter controlling both amplifier
channels engages.
TruPower limiting activity is indicated by the Limit LED
on the amplifier’s user panel. When it turns on, it shows
TPL activity that indicates when the safe power level is
exceeded (Figure 3.4).
Limiters cease operation when the power level and voltage
for the channel returns to normal, below the limiter’s
threshold. The limiting circuitry utilizes optical limiters that
add no noise and have no effect on the signal when the
limiter is not engaged and the LED is inactive.
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Figure 3.4. The 600-HP subwoofer’s Limit indicator
The 600-HP performs within its acoustical specifications
and operates at a normal temperature if the Limit LED is
lit for no longer than two seconds, and then goes off for at
least one second. If the limit LED remains on for longer than
three seconds, the 600-HP enters hard limiting with the
following negative consequences:
■
Increasing the input level will not increase the volume.
■
The system distorts due to clipping and nonlinear driver
operation.
■
The lifespan of the drivers is reduced because they are
subjected to excessive heat.
CAUTION:
While the limiters protect the
system under overload conditions and exhibit
smooth sonic characteristics, we recommend
that you do not drive the 600-HP into continuous
limiting. If an entire system of 600-HPs begins to
limit before reaching the required sound pressure
level (SPL), you should consider adding more
subwoofers to the system.
600-HP AMPLIFIER COOLING SYSTEM
The 600-HP uses a forced-air cooling system with two
fans (one primary and one reserve) to prevent the amplifier
module from overheating. The primary fan draws air in
through ducts on the front of the cabinet, over the heatsink,
and out the rear of the cabinet. Because dust does not
accumulate in the amplifier circuitry, its lifespan is increased
significantly. The front grille surface acts as an air filter for
the cooling system and should always be in place during
operation (Figure 3.5).
Figure 3.5. Airflow through the 600-HP
CAUTION:
When operating a weather-
protected 600-HP with the optional
collapsible cloth rain hood installed, always be
sure the rain hood is fully open. Leaving the hood
closed or partially open will limit the airflow through
the amplifier, which could cause it to overheat and
shut down. A clear, high-impact plastic quick-clip
rain hood comes standard with 600-HP weather-
protected version.
The variable-speed primary fan runs continuously with an
inaudible operating noise at its slowest speed. The primary
fan begins increasing speed when the heatsink reaches
42˚ C. The fan reaches full speed at 62˚ C and is barely
audible near the cabinet, even without an audio signal. In
the event that the heatsink temperature reaches 74˚ C, the
secondary fan turns on and is clearly audible without an
audio signal. The secondary fan turns on in response to:
■
Primary fan failure (check status immediately)
■
High source levels for a prolonged period
■
Accumulation of dust along the cooling path
The secondary fan turns off when the temperature
decreases to 68˚ C.