Peak limiting explained: true peak, ceilings and how not to squash a master

A peak limiter

If a peak would cross your chosen output limit, a peak limiter turns it down by just enough to hold it there. That output limit is called the ceiling. A limiter is a compressor, a processor that reduces signal above a set level, configured for very fast, firm peak control.

The difference is how firmly it responds. A compressor can reduce a peak without stopping it from rising further. A limiter acts in a few milliseconds or less to keep peaks within the ceiling. Signal below that limit passes untouched unless the limiter is already turning the gain down around a peak.

In mastering, the limiter sits last in the processing chain. Its job is to catch peaks at the output. Turning up its input while holding the ceiling is how limiting raises the track’s overall level.

How limiting raises the overall level

Imagine a track with brief peaks above a quieter body of sound. Raising the input lifts both. The limiter turns down peaks that would cross the ceiling, the maximum output level you set. Sound below that boundary passes without limiting, but now sits higher because you raised the input.

That is the trade: less headroom, the space available before peaks reach the ceiling, lets you raise the overall level. The limiter does not create loudness by lifting quiet details separately. You supply the increase at its input; it reduces the peaks that would otherwise exceed the boundary. This turning down is called gain reduction.

Sample peak and true peak measure different things

That boundary depends on what you measure. Sample peak is the highest sample value stored in the file. It tells you the largest recorded value, but not necessarily the highest point of the waveform reconstructed from those samples.

True peak is the estimated highest point of that reconstructed waveform, including points between samples. Defined in ITU-R BS.1770, it is measured using oversampling, which estimates additional points between the stored samples before checking the peak. The distinction matters because the waveform can rise above the highest stored sample.

On dense, bright material, true peak can exceed sample peak by a decibel or more. So a sample peak reading alone does not tell you how high the reconstructed waveform may reach. Lossy encoding, the compression used by streaming services, can add further overshoot beyond those peaks.

Why the ceiling belongs below 0 dBFS

A ceiling set at 0 dBFS leaves no margin for those overshoots. The ceiling is the output limit you set, and dBFS means decibels relative to digital full scale. Setting that limit below zero leaves headroom, a gap between your output peaks and full scale.

That gap gives the encoded version room for peaks to rise. It is not wasted level. It accounts for the fact that the file you deliver and the encoded version can have different peak levels. Apple's Digital Masters brief asks for headroom and warns that clipping, distortion from exceeding the available level, survives into the encoded version.

What ceiling do streaming platforms recommend

Spotify gives numerical recommendations for true peak, the estimated highest level of the reconstructed waveform between samples. These use dBTP, or decibels true peak. The ceiling is your set output limit.

• For a master at -14 LUFS, Spotify recommends true peaks no higher than -1 dBTP. LUFS means loudness units relative to full scale, measuring perceived loudness over time.
• For masters louder than -14 LUFS, Spotify recommends true peaks no higher than -2 dBTP.

Apple’s Digital Masters brief asks for headroom, meaning spare level below the maximum. It also warns that clipping already present in the master survives into the encoded version.

How attack, release and lookahead shape peak control

With the ceiling, or output limit, set, focus on timing. A limiter is a compressor with a very high ratio and a fast response. Attack describes how quickly it turns the signal down when a peak needs controlling.

Lookahead lets the limiter inspect the signal a few milliseconds before it reaches the output. It can begin turning down before a peak arrives, helping avoid clipping, where the first transient exceeds the available level.

Release sets how quickly the gain, or signal level, returns after a peak. Set it too fast and low notes can distort. Set it too slow and you can hear pumping, a rise and fall in level.

How to hear when limiting is too much

Use the same short passage to compare a lighter setting with the one you are considering. Turn the limiter input down, then bring it back up gradually. Listen for the point where extra level starts changing the sound in a way you do not want.

Gain reduction means how much the limiter turns the signal down. Its meter shows the work being done, but does not tell you whether the result suits the track. There is no single amount to choose from these recommendations. Judge the sound rather than chasing a gain reduction number.