Loudness is the most requested and most misunderstood part of mastering. A master has to compete with commercial releases - but pushing too hard destroys punch, clarity and dynamics. Understanding the tools, and how streaming services treat loudness, lets you find the right level for each record.
The gain reduction family
- Compressors reduce the level of signals above a threshold by a ratio, narrowing dynamic range. They can make quiet details more audible.
- Limiters are compressors with very high ratios - conventionally 10:1 and above - so that the signal barely rises above the threshold at all.
- Brick-wall limiters have an effectively infinite ratio. Nothing passes the ceiling. They react very fast but can distort audibly when pushed.
- Maximizers are brick-wall limiters with controls designed to preserve transients and reduce distortion as you push volume. A great maximizer is transparent - or adds a tonal character you choose.
- True peak limiters detect and control peaks between samples (intersample peaks), so the output never exceeds the ceiling even after conversion. They measure in dBTP and are the most accurate type - though they can change the texture of material with heavy clipping.
Key controls
- Input gain / threshold - how hard you drive the limiter. More drive means more loudness and more gain reduction.
- Ceiling (output) - the maximum output level. Set it and leave it for a given format (see below).
- Release - how quickly gain reduction recovers. Fast releases sound louder but can distort and pump; slow releases are smoother but can flatten transients. Many maximizers have automatic release modes.
- Lookahead - lets the limiter see peaks coming. Short lookahead preserves transients better.
- Character or style modes - different algorithms for transparency, punch or aggression.
- Stereo link - whether left and right are limited together or independently.
How far to push
Watch the gain reduction meter and listen closely to:
- Transients - do drums lose their snap?
- Low end - does the bass start to distort or pump the mix?
- Density - does the mix become flat and tiring?
As a rough guide, a few decibels of gain reduction from a good maximizer is usually transparent; heavy limiting needs a mix built for it. Spreading loudness across stages - gentle compression and saturation before the limiter, or more than one limiter in series - often sounds cleaner than one limiter working very hard. (See the bonus chapter on mirroring loudness maximizers.)
Loudness and streaming normalisation
Streaming services measure the integrated loudness of every track and adjust playback so tracks play at similar levels. Spotify's default reference is -14 LUFS, YouTube's is similar, and Apple Music normalises to around -16 LUFS. A master louder than the reference is turned down; a quieter one may or may not be turned up, depending on the platform and its headroom.
What that means:
- Extreme loudness brings no advantage on streaming - a crushed master is simply turned down, and sounds smaller than a dynamic one at the same playback level.
- But genre expectations still matter. Many commercial pop, hip-hop and EDM masters are far louder than -14 LUFS, because density and energy are part of the sound - and because DJs, clubs, radio and downloads do not normalise.
- Master for the music, not the number. Match your references, check how the master sounds after normalisation (many meters simulate it), and avoid destroying dynamics for loudness no one will hear.
Ceiling and true peak
Lossy encoding and playback conversion can create peaks above 0 dBFS. To leave room:
- A ceiling of -1 dBTP is a common and safe choice for streaming. Spotify recommends -1 dBTP, or -2 dBTP for masters louder than -14 LUFS.
- Some engineers use around -0.3 dBFS for CD and lossless formats.
Do this now
- Put a maximizer on a premaster and push it until you hear transients suffer. Back off until they return.
- Note the integrated LUFS, true peak and crest factor of your master and of your reference.
- Use a normalisation preview to hear both at -14 LUFS. Which sounds bigger?
Adapted, with thanks, from the lesson notes of J.M. Brooklyn Audio Mastering.