The Limiter

Holding peaks without changing tone, and what lookahead, release and true peak each do.

Related

True-Peak LimiterClippingDrum Kit

The question

A limiter sits at the end of the chain, keeping peaks under a ceiling while changing tone as little as possible. It is not a compressor, which works on average level.

How it works

A limiter uses a very high ratio and a short attack to pull down whatever exceeds the ceiling. Modern plugins look ahead and apply a smoothed gain envelope, so the result is not an instant square wave. True-peak detection needs oversampling, since a peak between sample points can sit above the meter. Release sets how fast gain returns and whether the low end pumps.

Settings and what you hear

Set the ceiling near minus 1 dBTP to leave room for encoding, and add 1 to 3 dB of drive. A release of 50 to 200 ms suits most material; a shorter one makes every kick pull the mix down. Longer lookahead flattens transients more.

What to listen for

Play a slow rock drum loop and listen to the snare edge, then push the gain by 3 dB. The snare moves from impact to sitting against the ceiling, while the kick makes the rest dip and recover. On dense orchestral music, listen for a sandy edge on brass tuttis.

Common misconceptions

That a limiter can push loudness without limit; that a ceiling at 0 dBFS prevents clipping; that limiting changes only peaks and never density.

Sources

• Giannoulis, Massberg and Reiss, Digital Dynamic Range Compressor Design, JAES 2012 — limiter topology checked, not quoted
• ITU-R BS.1770-4, Algorithms to Measure Audio Programme Loudness and True-peak Level — true-peak method checked, not quoted

Used for fact-checking only; all prose is original.