MACKIE M1400/M1400i - Manual (Page 21)

21
simply stops. This causes a sine wave to
“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 and cause
distortion. It just takes a
stronger signal to do it. So even with the LIM-
ITER turned on, you should still pay attention
to the
OL LEDs .
SUBWOOFER
Here’s a special surprise: If you bought the
M•1400/M•1400i amplifier to power a
subwoofer system, you just saved yourself the
cost of a crossover! The M•1400/M•1400i amp
has an active
SUBWOOFER filter built in. You
can use it, along with the variable LOW CUT
FILTER in a second M•1400/M•1400i, to re-
produce 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•1400/M•1400i’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. Make sure the LOW CUT FILTER is set to
OFF or nearly OFF. If it is turned up above
the subwoofer cutoff frequency, the output
from the amplifier will be greatly diminished.
5. Connect your cords and speaker cables as
usual (see “Quick Start” on page 4). Set
the AMP MODE to either STEREO,
MONO, or BRIDGE, depending on your
application. (
STEREO and MONO operate
the same with SUBWOOFER activated).
6. Turn the M•1400/M•1400i’s POWER on.
Woof!
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
6k Hz 2k Hz
MONO
(CHS SUMMED)
BRIDGE
LIMITER (CH1 & CH2)
OFF
FULL
RANGE
SUB
WOOFER
LOW CUT
FILTER
LOW CUT
FILTER
OUTPUT APPLICATION
BALANCED
OR
UNBALANCED
BALANCED
OR
UNBALANCED
ON
/ BRIDGE / MONO
170 Hz OFF
4.5k Hz
6k Hz 2k Hz
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