What Does a Limiter Do? Threshold, Ceiling and True Peak Explained

A limiter is a fast, aggressive compressor that stops your audio from ever passing a set ceiling, while letting you push the overall level up underneath it. In mastering it does two jobs at once: it protects you from clipping by holding a hard ceiling, and it raises loudness by catching the peaks so the rest of the track can come up. Set the ceiling to -1 dBTP, raise the input until you reach your loudness target near -14 LUFS for streaming, and stop before the track starts to sound flat.

What a limiter actually does to the signal

Think of a limiter as a wall your audio cannot cross. When a peak tries to go above the ceiling you set, the limiter instantly reduces its gain so it stops exactly at the wall. Because it catches those peaks, you can turn the whole signal up without the peaks clipping - and turning everything up is what makes the track louder. So a limiter does not just prevent overs; it is the tool that raises your master to a competitive loudness. This is why the limiter is the last processor in almost every mastering chain: it sets the final level and the absolute ceiling in one move.

A brickwall limiter, the kind used in mastering, guarantees nothing ever exceeds the ceiling. That guarantee is what makes it safe to push loudness right up to the edge.

Threshold: where limiting starts

The threshold is the level at which the limiter begins working. Anything above the threshold gets limited; anything below passes untouched. On many mastering limiters the threshold is combined with an input or gain control - lowering the threshold is effectively the same as raising the input, because both push more of your signal above the limiting point.

The lower you set the threshold, the more of the signal gets caught and the louder the track becomes - but also the harder the limiter works, and the more you risk audible damage. The threshold is your loudness lever, and it is the control you move to hit your LUFS target.

Ceiling: the hard limit

The ceiling, sometimes called the output ceiling, is the absolute maximum level the limiter will allow. Nothing gets past it. This is your clipping protection. For mastering, set the ceiling to -1 dBTP - one decibel below true-peak full scale. That headroom does two things: it stops inter-sample peaks from clipping on consumer converters, and it protects the file when streaming platforms transcode it into lossy formats like AAC and Ogg Vorbis, which can nudge peaks slightly higher than your original. Master right up to 0 and lossy encoding can push it over, adding crackle that was never there.

Gain and input: how you drive it

The input or gain control determines how hard you hit the limiter. Turn it up and more of your signal crosses the threshold, so more limiting happens and the track gets louder. This is the control you ride while watching your LUFS meter. Raise it slowly until your integrated loudness lands near target, then listen closely - the last dB of gain is where masters usually go wrong. If the track stops getting louder and starts getting flatter, you have passed the useful point.

What is true peak and why it matters here

A normal peak meter reads the level of individual samples. But when a digital-to-analog converter reconstructs the waveform between those samples, the actual analog peak can rise higher than any single sample - an inter-sample peak. A true-peak limiter, set to a dBTP ceiling, measures and catches those reconstructed peaks, not just the samples. That is why you set the ceiling in dBTP rather than dBFS: it guarantees the real, reconstructed signal stays under the line, not just the sample values. Always enable true-peak mode on a mastering limiter. For the loudness side of the same coin, read what LUFS to use for streaming.

How to use a limiter in mastering

Here is a reliable workflow:

• Place it last. The limiter goes at the very end of your chain, after EQ, compression and any tone shaping.
• Set the ceiling to -1 dBTP with true-peak mode on.
• Raise input gain slowly while metering integrated LUFS across the whole song, aiming near -14 LUFS for streaming.
• Watch the gain reduction meter. A few dB on the loudest moments is normal. Constant heavy reduction means you are pushing too hard.
• Listen for damage: pumping, dulled transients, a bass that stops punching, a stereo image that shrinks. Any of these means back off.

Limiter vs compressor: what is the difference?

A compressor gently reduces dynamic range with a lower ratio and slower response - it shapes and glues. A limiter is compression taken to the extreme: a very high ratio and near-instant response so nothing crosses the ceiling. In a full master you often use both - a compressor for cohesion earlier in the chain, then a limiter at the end for loudness and protection. They are complementary, not interchangeable.

Common limiter mistakes

• Pushing too hard for loudness that gets normalized away. Streaming turns loud masters down, so past target you only lose punch. See how loud a master should be.
• Setting the ceiling to 0 dBFS, which invites inter-sample and lossy-encoding clipping. Use -1 dBTP.
• Metering a loop instead of the whole song, which reads too hot and leads to over-limiting.
• Trying to fix a weak mix with the limiter. If the track sounds small, the answer is usually in the mix, not more limiting - see why your song sounds quiet.

A limiter is a finishing tool, not a loudness cannon. Used with intent - ceiling at -1 dBTP, input raised only until you hit target - it delivers a loud, clean master. Pushed blindly, it flattens everything you worked for. For the full chain around it, read how to master a song and browse the mastering guides.