MACKIE M1200/M1400 - Manual (Page 21)

21
“square off,” and the average power going into
the speaker is roughly double that of a sine
wave. Square waves sound awful, and could
possibly damage your speakers and/or your
reputation.
The LIMITER is especially handy when
you’re working with loud output levels. Having
the signal spikes (kick drum, for instance) at-
tenuated a bit can actually increase the
apparent loudness of the overall mix without
diminishing the “power” behind the spikes.
Be Forewarned: With the
LIMITER engaged, you can
still overdrive the amplifier
into clipping. It just takes a
stronger signal to do it. So
even with the LIMITER turned on, you should
still pay attention to the OL LEDs .
SUBWOOFER
Here’s a special surprise: If you bought the
M•1200/M•1400 amplifier to power a subwoofer
system, you just saved yourself the cost of a
crossover! The M•1200/M•1400 amps have an
active
SUBWOOFER filter built in. You can use
it, along with the variable LOW CUT FILTER
in a second M•1200/M•1400, to reproduce the
function of a crossover.
20 Hz 100 Hz 1k Hz 10k Hz 20k Hz
–15 dB
–10 dB
–5 dB
0
dB
5 dB
Since most low-frequency energy is mono-
phonic (the same in both channels), the
subwoofer circuit takes the signal from both
Channels 1 and 2 and sums them together. This
summed signal is then directed to both power
amplifier output stages. It doesn’t matter
whether the
AMP MODE switch is set to
STEREO, MONO, or BRIDGE, it will sum the
inputs when the
OUTPUT APPLICATION
switch is set to SUBWOOFER.
Here’s how to configure it:
1. Turn the M•1200/M•1400’s POWER off.
2. Set the OUTPUT APPLICATION switch
to SUBWOOFER.
3. Select a rolloff point, via the FREQUENCY
switch: At “125Hz,” you’ll get the low
sub-harmonics on up to the audible bass
range. At “63Hz,” you’ll get just the lowest
frequencies, more to be felt than heard.
You’ll probably want to try this switch both
ways.
4. Connect your cords and speaker cables as
usual (see “Quick Start” ). Set the AMP
MODE to either STEREO, MONO, or
BRIDGE, depending on your application.
(
STEREO and MONO operate the same
with SUBWOOFER activated).
5. Turn the M•1200/M•1400’s POWER on.
Woof!
If you want to use a second M•1200/M•1400
to reproduce the rest of the audio range, follow
this procedure:
1. Connect the
THRU jacks on the first
subwoofer amplifier to the INPUT jacks
on the second amplifier.
2. With POWER off, set the OUTPUT
APPLICATION switch on the second
amplifier to FULL RANGE (LIMITER either
ON or OFF).
CHANNEL
2 1
CHANNEL
63Hz
125Hz
CONSTANT DIRECTIVITY
HORN EQ /AIR EQ
CONSTANT DIRECTIVITY
HORN EQ /AIR EQ
INPUT
THRU THRU
INPUT
AMP MODE
FREQUENCY
4.5 k Hz
ON
5.6k Hz 2k Hz
MONO BRIDGE
LIMITER (CH1 & CH2)
OFF
FULL
RANGE
SUB
WOOFER
LOW CUT
FILTER
LOW CUT
FILTER
OUTPUT APPLICATION
BALANCED
OR
UNBALANCED
BALANCED
OR
UNBALANCED
AIR EQ
ON
/ BRIDGE / MONO
170 Hz OFF
4.5k Hz
5.6k Hz 2k Hz
AIR EQ
170 Hz
100 Hz
OFF
STAGE
MONITOR
100 Hz
STAGE
MONITOR
OFF
TYPICAL
ON
OFF
TYPICAL
TYPICAL
35 Hz
TYPICAL
35 Hz
STEREO
TYPICAL
STEREO
TYPICAL
AIR EQ AIR EQ
Subwoofer Filter