Mackie M1400/M1400i Owner's Manual - Page 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) attenuated 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 LIMITER 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 reproduce the function of a crossover. 5dB 0dB Since most low-frequency energy is monophonic (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! -5dB -10dB -15dB 20Hz 100Hz 1kHz 10kHz 20kHz Subwoofer Filter 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 21