Compressor/Limiter Setup Adjustments Dynamics

There's no universal "correct" attack or release setting — it depends entirely on what job the compressor is doing, protection versus musical leveling. Reference SRH-COMP-SETUP-01. Below is the general logic for dialing in attack and release, followed by a worked numeric example for setting threshold and ratio when the job is protecting speakers from an amp that can put out more power than they can survive.

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Key facts

Attack too fast: the compressor tries to ride the actual waveform, producing unnatural level jumps and audible distortion, especially on low frequencies.
Attack too slow: the output overshoots your intended ceiling before the compressor reacts — the peak gets through before gain reduction engages.
Release too fast: pumping/breathing as gain recovers rapidly.
Release too slow: quiet passages stay squashed because the gain hasn't recovered from the last loud hit yet.
Protection/limiting use: push attack and release as fast as you can get away with before it sounds audibly wrong.
Musical leveling use (vocals, sustain): use the slowest attack that still keeps peaks under control, for more natural punch and dynamic range.
Worked example ceiling: a speaker rated 100 W continuous / 200 W peak, driven by a 200 W amp (rated at +4 dBu input) with its input attenuator backed off 10 dB, hits its power ceiling at a +14 dBu signal — that's your hard output limit for the compressor/limiter to enforce.
Setting threshold at +10 dBu against a worst-case +26 dBu input works out to roughly a 4:1 compression ratio; tightening the threshold to +13 dBu works out to roughly 13:1 — more brick-wall, less natural.

Set the Foundation

Adjust the compressor's input level control (if it has one) so the incoming signal sits comfortably above the noise floor without clipping the input stage. Decide the job before you touch threshold or ratio: are you protecting gear (limiting/brick-wall behavior) or shaping the performance (leveling vocals, adding sustain)? Everything downstream depends on that answer.

Worked Example — Threshold & Ratio for Speaker Protection

Establish the mechanical ceiling: say a speaker is rated 100 W continuous / 200 W peak, and the amp feeding it is rated to deliver 200 W into that load given a +4 dBu input. Factor in the amp's actual input attenuator setting — if it's been turned down 10 dB from that +4 dBu reference, it now takes a +14 dBu signal at the amp input to reach the full 200 W. That +14 dBu figure becomes the hard ceiling the compressor/limiter must never let through (assuming the compressor itself is set for unity gain when idle). To keep as much natural dynamic range as possible, set the threshold a few dB under that ceiling rather than right at it — for example, +10 dBu, leaving 4 dB of headroom up to the +14 dBu limit. Estimate the hottest signal that could realistically hit the compressor's input — say +26 dBu worst case — and subtract the threshold: +26 - +10 = 16 dB of signal that's above threshold and needs taming. Divide that 16 dB of overshoot by the 4 dB of output movement you're willing to allow (threshold to ceiling): 16:4 simplifies to roughly a 4:1 compression ratio — that's what keeps the output pinned under +14 dBu across the whole range of expected input levels. For comparison, pulling the threshold in tighter to +13 dBu only leaves 1 dB of allowed output movement (+14 minus +13) against that same worst-case 13 dB of overshoot (+26 minus +13) — a much steeper roughly 13:1 ratio. That's usable as pure brick-wall protection, but it sounds harsher because the whole effect slams in at once rather than gradually.

Dial In Attack and Release by Ear

With real program material playing, watch a meter or scope while you adjust attack. For pure protection/limiting, push it as fast as it'll go without audible distortion creeping in. For musical leveling — riding vocals, adding sustain to a guitar — back the attack off as slow as you can while still keeping the level under reasonable control. Letting more of the transient through preserves punch and makes the compression feel more natural. Set release slow enough that you don't hear obvious pumping or breathing as the gain recovers, but fast enough that a quiet passage right after a loud one isn't left sounding ducked and lifeless.

Source: Davis, Gary D. & Jones, Ralph. The Sound Reinforcement Handbook, 2nd ed. (Hal Leonard/Yamaha). Section 14.3.3, pp.272-273. Rewritten in Ryan's own words from the source material.