A downward compressor reduces gain above the threshold. It does not automatically make quiet parts louder. After louder parts have been reduced, Makeup can raise the overall result so that sustain is more audible. Noise rises too.
Threshold sets where compression begins; Ratio sets its strength. Under ideal, steady-state hard-knee conditions, Lout = T + (Lin−T)/R for Lin > T. With T=−20, input −12, and R=4, the output is −18 dB before Makeup. A 4:1 ratio does not divide the entire amplitude by four. During transients, Attack, Release, and Knee change that response.
Attack sets how quickly the compressor responds to a level increase. It does not postpone the sound by that fixed duration. A fast Attack catches more of the transient; a slower Attack preserves more of the pick. Release sets gain recovery, rather than sustain duration. Too fast can add modulation or distortion; too slow can leave the next note compressed.
Makeup balances the level after compression. If the compressor precedes drive, Makeup also pushes the next drive stage. Blend mixes dry and compressed signals to help preserve transients. Knee shapes the transition around the threshold; the Rigs Compressor uses a fixed soft knee, without a separate Knee knob.
Adjust while playing quiet and hard attacks and sustained notes: set Threshold/Ratio, listen to Attack, match Release to the playing pattern, then level-match Makeup. More audible sustain is not a new note or unlimited string vibration. A compressor does not have to remove all dynamics, and it does not guarantee an output without peaks.
Control concept reference: FabFilter — Basic Compressor Controls. See Compressor controls for Rigs parameter ranges.
Concept references
Threshold, Ratio, Makeup
Does 4:1 mean that every level is divided by four?
- Inspected input
- -12.0 dBFS
- Output
- -18.0 dBFS
- Gain reduction before makeup
- 6.0 dB
Only the portion above threshold follows the 4.0:1 ratio. Makeup then raises the entire result.
A steady-state hard-knee curve. Gain reduction is calculated before makeup. The native pedal attack, release, and knee are not simulated here.
Attack and Release
Why does compressor attack serve a different purpose from Auto Swell?
- Response after 1 × attack
- 63.2%
- Remaining after 1 × release
- 36.8%
- Context
- Level follower
A follower responds to rising level with attack and falling level with release. In a compressor, it controls gain reduction rather than a volume that always rises.
A static curve whose target starts at 100 ms and stops at 800 ms. The model reaches 63.2% at one time constant; native dial values do not necessarily use that definition.