Software Instruction Manual

IQ–MSD Turbo 1.4 Advanced IQ System Software
Page 151
6.4.5 Output Compressor/Limiter Function
(Figure 6.13) Even if every input is compressed, there is still a chance that the mix might become too loud. The
Output Compressor/Limiter function keeps the output from exceeding a predetermined level. It’s especially
valuable when used as an output limiter for the protection of amplifiers, loudspeakers and other audio equipment.
It works in a very interesting way. Instead of compressing the signal on the mixing bus, it compresses the signal
at each input. Compression occurs only when the mix exceeds the Limit Threshold. It doesn’t matter how loud a
particular input gets, the mix which feeds each output channel must exceed the Limit Threshold before compres-
sion occurs.
The controls that configure the Output Compressor/Limiter function are very similar to those of the Input Compres-
sor/Limiter function.
Compressor/Limiter: The Output Compressor/Limiter function is turned on and off with this control.
Limit Threshold: The Limit Threshold control sets the peak signal level above which compression occurs.
If the mixer is connected to audio equipment that has a specified maximum input voltage, it is easy to limit the mixer’s
output to that level. If the specified input level were 0 dBu (0.775 V), the Limit Threshold could be set to 0 and the
Compression Ratio set to
∞:1. In practice, this is a little harsh. A Limit Threshold of –2 dBu with a Compression
Ratio of 16:1 will attenuate an incoming signal 32 dB before the output level reaches 0 dBu. When used with the
Input Compressor/Limiter, the Output Compressor/Limiter provides some of the most accurate and predictable
audio system protection available today.
Tip: If you’re not sure where to set the Limit Threshold, press 2 to view the bar graph display. The yellow bars
above OUT 1 and OUT 2 represent the instantaneous peak output levels.
Compression Ratio: The Compression Ratio control sets the amount of compression applied for every step
over the Limit Threshold. For example, when a 4:1 compression ratio is applied to a signal that exceeds the Limit
Threshold by 20 dB, the signal is attenuated 15 dB. When an infinite compression ratio (
∞:1) is chosen, the
Fig. 6.13 The Fourth SMX-6 Sub-block Screen