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CD Frequency
Your compression drivers’ spec sheet should
have a suggested frequency for compensation
boost. If so, just turn the
CONSTANT DIREC-
TIVITY
switch
ON
and set its knob to match
that frequency. If your spec sheet doesn’t have
that information, you can simply adjust the
Frequency knob by ear, preferably using the
same music as the actual performance (3.5kHz
is a good place to start).
100
Hz
1k
Hz
20
Hz
10k
Hz
20k
Hz
–5
dB
0
dB
5
dB
15
dB
10
dB
Wait, there’s more: If you don’t have con-
stant directivity horns, you can forget all this,
and leave the switch
OFF
.
Or, better yet, you can use this
CONSTANT
DIRECTIVITY
feature to enhance your EQ
curve. By setting the Frequency knob fully
clockwise, you introduce a very high frequency
boost to the signal (above 6kHz). And in
Mackie-land, this gentle boost has a name:
AIR
,
as seen on our SR series of consoles. By boost-
ing these high frequencies,
AIR
will breathe
life into your mix, making cymbals brighter
and vocals silkier.
Speaking of Mackie SR consoles: If you use
both the
AIR
feature on an SR console as well
as the
AIR
feature just described on the
M•1200/M•1400, you may be overdoing it. You
won’t hyperventilate or anything, but it might
cause your audience to experience ear fatigue
from too much high-frequency content. Too
much of a good thing, perhaps.
CHANNEL
2
1
CHANNEL
63Hz
125Hz
CONSTANT DIRECTIVITY
HORN EQ /AIR EQ
CONSTANT DIRECTIVITY
HORN EQ /AIR EQ
INPUT
THRUTHRU
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
More on Constant Directivity Horns
Back in the early ’70s, radial
horns were the common
mechanism for reproducing
high frequencies. Radial
horns had a serious problem,
though. The high frequencies
tended to beam straight ahead, so if you moved
away from front and center (off-axis), the bril-
liance and sizzle quickly diminished to a
muffled blur. Constant Directivity horns were
designed to spread the higher frequencies
evenly throughout the horn’s dispersion pattern.
This was accomplished by using a smaller
opening to the horn, using straight sidewalls in
both the horizontal and vertical planes (radial
horns typically have curved vertical sections
that cause beaming), and providing a flare at
the mouth of the horn to disperse the mid to
high frequencies.
All high-frequency compression drivers have
an inherent roll-off of about 6 dB per octave
above about 3kHz. The exact frequency at
which the roll-off occurs (called the mass
breakpoint) depends on the materials used,
the mass of the moving parts (diaphragm and
voice coil) and the strength of the magnet. The
CONSTANT DIRECTIVITY HORN EQ
control
on the M•1200/M•1400 compensates for this
natural roll-off in the power response of the
compression driver coupled to a CD horn, with
the end result of flat-frequency response (con-
stant) with a wide coverage angle (directivity).
AMP MODE
This three-way switch, along with the
OUT-
PUT APPLICATION
’s three-way switch,
determines what kind of amplifier you want
the M•1200/M•1400 to be.
Constant Directivity EQ