172 | Chapter 13—Dynamics Processors | |
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| | Parameter | Range | |
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| | THRESHOLD | –54 dB to 0 dB (55 steps) | |
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| | OUT GAIN | –18 dB to 0 dB (0.5 dB steps) | |
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| | WIDTH | 1 dB–90 dB (1 dB steps) | |
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| | ATTACK | 0–120 ms (1 ms steps) | |
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| | RELEASE | 5 ms–42.3 s (fs = 48 kHz) | |
| | 6 ms–46 s (fs = 44.1 kHz) | |
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| | RATIO | 1:1, 1.1:1, 1.3:1, 1.5:1, 1.7:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 5:1, 6:1, 8:1, | |
| | 10:1, 20:1 (15 steps) | |
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THRESHOLD—This determines the input signal level at which compression and expansion are applied. Signals at a level below the sum of the threshold and width are attenuated by the expander. Signals at and above the threshold level are compressed by the amount specified using the Ratio parameter. The trigger signal is sourced using the KEY IN parameter.
OUT GAIN—This sets the compander’s output signal level. It can be used to compensate for the overall level change caused by the compression and expansion processes.
WIDTH—This determines how far below the threshold level expansion is applied. The expander is essentially turned off when the width is set to 90 dB.
ATTACK—This determines how soon the signal is compressed and expanded once the compander has been triggered. With a fast attack time, the signal is companded almost immediately. With a slow attack time, however, the initial transient of a sound passes through unaffected. Attack times from 1 to 5 milliseconds are a good place to start.
RELEASE—This determines how soon the compressor and expander return to their normal gains once the trigger signal level drops below the threshold. If the release time is too short, the gain will recover too quickly causing level pumping (i.e., noticeable gain fluctuations). If it is set too long, the compressor may not have time to recover before the next high level signal appears, and it will be compressed incorrectly. Release times from 0.1 to 0.5 seconds are a good place to start.
RATIO—This determines the amount of compression. That is, the change in output signal level relative to change in input signal level. For a 2:1 ratio, for example, a 10 dB change in input level (above the threshold) results in a 5 dB change in output level. For a 5:1 ratio, a 10 dB change in input level (above the threshold) results in a 2 dB change in output level. The expander ratios are fixed: 1.5:1 for the soft compander (S) and 5:1 for the hard compander (H).