Mackie M800 Owner's Manual - Page 17

LIMITER LIMITER ON (TYPICAL). This is the normal configuration with protective limiting. LIMITER OFF is without protective limiting. The limiter is not designed to alter your sound - it's just there to protect your speakers from the effects of clipping. Its effect is virtually transparent, meaning you probably won't even notice any audible difference. We recommend that you leave it engaged, hence the TYPICAL label below it. If you're working at quiet levels all the time, or you've already placed a compressor/limiter in the signal path, or if you just hate compression, you can leave the limiter out of the circuit. By design, the limiter is out of circuit when not called upon. The limiter works independently on each channel. It senses when the amplifier channel is about to be overdriven and attenuates the overall level just enough to keep the signal from clipping. Clipping occurs when the output voltage no longer linearly follows the input voltage and 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. Sample Audio signal As the amplifier output voltage increases, it will eventually run into the internal DC power supplies and start to flatten out. The flat tops represent a DC voltage reaching your speakers, which interrupts the natural movement of the speaker's voice coil. High frequency harmonics are also produced which can play havoc with your tweeters. Speakers are designed to handle good clean continuous signals, but give them a clipped signal and even high powered speakers can be damaged. For example, a 100 watt amplifier that is clipping, can damage speakers that are rated at 400 watts. 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. It is also a useful protection device for those unexpected moments, such as a mike stand falling over, dropping the tone arm, or an attack of killer feedback. 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 must pay attention to the OL LEDs. AC volts AC volts Clipped Audio signal Clipped 'do time V+ 0 V- time 17