Cd Frequency; Constant Directivity - Mackie M-800 Owner's Manual And Warranty Registration
Fr series fast recovery high-current power amplifier
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Also See for M-800:
- Hook-up manual (4 pages) ,
- Brochure (8 pages) ,
- Service manual (22 pages)
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CONSTANT DIRECTIVITY SWITCH
If you don't have constant directivity horns,
you can leave this switch OFF.
Compression drivers mounted on constant-
directivity horns require compensation in the
form of a high-frequency boost, with its "knee"
set somewhere between 2kHz and 6kHz. Until
now, you'd have to resort to external crossovers
or worse yet, graphic EQ modules. Both of
these are fraught with limitations, not to men-
tion adding cost, rack space requirements, and
complexity to your system.
The M•800 power amplifier eliminates the
need for any of these external devices — it has
the compensation circuitry already built in,
and using it is a breeze.
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).
15
dB
10
dB
5
dB
0
dB
–5
dB
20
100
Hz
Hz
Constant Directivity EQ
Even if you don't have CD horns, you can
use the CONSTANT DIRECTIVITY feature to
enhance your EQ curve. By setting the fre-
quency 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 boosting these high frequencies,
AIR will breathe life into your mix, making
cymbals brighter and vocals silkier.
Speaking of Mackie SR consoles: If you use
the AIR feature on an SR console as well as the
AIR feature just described on the M•800, you
may be overdoing it. You won't hyper-ventilate
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.
exact frequency at which the roll-off occurs
(called the mass breakpoint) depends on the ma-
terials 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•800 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) over a wide coverage angle (directivity).
1k
10k
20k
Hz
Hz
Hz
CONSTANT DIRECTIVITY
HORN EQ /AIR EQ
4.5k Hz
OFF ON
2k Hz
6k Hz
AIR EQ
TYPICAL
More on Constant
Directivity Horns
All high-frequency compres-
sion drivers have an inherent
roll-off of about 6 dB per oc-
tave above about 3kHz. The
15
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