Lexicon MPX 550 manual Compressor

MPX 550

Basic Operation

THE COMPRESSOR

The compressor is available in all programs, except Dynamics. (Dynamics uses a different compression mechanism, explained on page 4-33.) The compressor sits in the wet component of the signal in front of the effects in the loaded program. It is controlled with four parameters: CmpRatio, Threshld, CmpAttk, and CmpRels. These parameters are located on the last Edit Page for each program, except those in the Cmprssr Bank.

The ratio (CmpRatio) parameter can be set to ratios of 1:1 (off), 2:1, 3:1, 4:1, 5:1, and 10:1. The threshold (Threshld) parameter can be set within a 0 to -32dB range. These settings are relative to 0dBFS (digital saturation). The compressor is disabled if either the ratio parameter is set to 1:1 or the threshold parameter is set high enough to prevent the incoming signal from crossing the compression threshold.

The attack (CmpAttk) and release (CmpRels) parameters determine how fast the compressor responds, within 3dB of the output level dictated by the incoming signal.

For most music material, the release time should be about four times longer than the attack time. Both must be long enough to accommodate the bass content of the music.

If the compressor is set to react faster than the waveform of the music itself, the resulting changes in output level will re-shape the waveform enough to produce undesirable audio effects. For example, 80Hz has a period of 12ms. If this is a dominant component in the music, set both the attack and release parameters to at least 12ms, even higher for better results. The compressor acts on both the left and right channels at the same time, using the sum of the two channels as its trigger.

Compression presets are available in the Cmprssr Bank (see page 4-31). For other compression-only effects, send compressor output into a Dly/Eko program with the Delay parameter set to 0. The compressor does not add propagation delay to the audio path. (Note the converters introduce about 2ms of propagation delay.)

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