Mackie M1400/M1400i Owner's Manual - Page 19

CD Frequency Your compression drivers' spec sheet should have a suggested frequency for compensation boost. If so, just turn the CONSTANT DIRECTIVITY 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). 15dB 10dB 5dB 0dB -5dB 20Hz 100Hz 1kHz Constant Directivity EQ 10kHz 20kHz Wait, there's more: If you don't have constant 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 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 both the AIR feature on an SR console as well as the AIR feature just described on the M•1400/M•1400i, 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. 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 brilliance 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•1400/M•1400i 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 (constant) with a wide coverage angle (directivity). AMP MODE This three-way switch, along with the OUTPUT APPLICATION's three-way switch, determines what kind of amplifier you want the M•1400/M•1400i to be (or not to be - what was the question?). 1 CHANNEL / BRIDGE / MONO LOW CUT INPUT FILTER TYPICAL 35 Hz BALANCED OR UNBALANCED STAGE MONITOR 100 Hz OFF 170 Hz CONSTANT DIRECTIVITY HORN EQ /AIR EQ 4.5 kHz ON 2k Hz 6k Hz AIR EQ OFF TYPICAL THRU AMP MODE STEREO MONO BRIDGE TYPICAL (CHS SUMMED) OUTPUT APPLICATION FULL RANGE LIMITER (CH1 & CH2) STEREO TYPICAL SUB WOOFER FREQUENCY 125Hz ON OFF 63Hz INPUT BALANCED OR UNBALANCED 2 CHANNEL LOW CUT FILTER TYPICAL 35 Hz STAGE MONITOR 100 Hz OFF 170 Hz CONSTANT DIRECTIVITY HORN EQ /AIR EQ ON 4.5k Hz THRU OFF TYPICAL 2k Hz 6k Hz AIR EQ 19