MACKIE HR824 - Manual (Page 12)

12
OL
PWR
ON
FRONT PANEL DESCRIPTION
Overload Protect
The high and low frequency power amplifiers
have clipping detectors that light the OL LED
when either power amplifier output clips.
• If you see the
OL LED blinking more than
just occasionally, it’s an indication that you
should reduce the signal level coming from
your mixer or other signal source.
• If frequent clipping continues, the driver
thermal overload protection activates a
compressor that reduces the input level to
the amplifiers. During this time the
OL
LED lights continuously.
• The compressor was designed to protect
the speakers and its action is highly
audible.
• The compressor was not designed for
mixing!
If a client insists on listening
to the monitors at a very high
volume, you may find that
the
OL LED lights frequently.
Since the majority of the
power requirement in any monitor are the low
frequencies, selectively reducing the low end
can provide a little more headroom and volume
for the monitors. Change the
LOW FREQ
switch to 47Hz or 80Hz, if necessary, to reduce
the bass response. This may allow the HR824s
to play just enough louder to satisfy the client
and to eliminate most of the amplifier clipping.
Power Switch
Use this switch to turn on or off the HR824
from the front. It works with the POWER
MODE switch on the rear panel in the
following way:
• If the
POWER MODE switch on the rear
panel is set to STANDBY, the front panel
power switch has no effect. The PWR
LED remains off.
• If the POWER MODE switch is ON, the
front panel power switch turns the HR824
on or returns it to
STANDBY mode, as
indicated by the PWR LED.
• If the POWER MODE switch is in the
AUTO ON position, the front panel power
switch turns the HR824 on as long as there
is a signal present.
OL (Overload) LED
This LED blinks when the amplifiers begin
to clip and lights steadily if the overload protec-
tion circuit
has been triggered.
• Occasional blinking of the OL LED indi-
cates that the loudest transients are
reaching the maximum output capability of
the amplifiers. This is okay.
• Frequent or continuous blinking of the OL
LED indicates that you have exceeded the
maximum output capability of the amplifi-
ers and that the amplifiers are clipping. If
you persist, the overload protection circuit
takes over, reducing the input level. You
should reduce the level from your signal
source until the
OL LED blinks occasionally
or not at all.
PROTECTION CIRCUITS
There are a number of protection mecha-
nisms designed into the HR824 to safeguard
the loudspeakers from inadvertent damage.
CAUTION: The protection circuits are de-
signed to prevent damage to the loudspeakers
under reasonable and sensible conditions.
Should you choose to ignore the warning signs
(i.e., frequent Overload LED indications, ex-
cessive distortion), you can still damage the
speakers in the HR824 by overdriving them
past the point of amplifier clipping. Such dam-
age is beyond the scope of the Warranty.