The limiter - compressor with a high ratio

The Limiter / Brickwall Limiter has some functions that need to be understood. Here is a brief overview of what we want to go into in more detail in the following text:

  • Limit
  • Brick wall limiters
  • Threshold
  • Attack
  • Release
  • Knee or soft knee
  • applications

Limit

What does a limiter do?

The conventional limiter usually works like a Compressor. Only this one works with one much higher ratiothan is usually the case in audio compression (parallel compression is excluded). Therefore, the limiter is also referred to as a high-ratio compressor. As a rule, audio material is limited in the Ratio 10: 1 to infinity: 1. The audio signal is sent to the limiter, which is usually located in the master channel of a mix or as the last link in the Mastering chain. Whether as a plug-in from Waves, Fabfilter or Brainworx, or as hardware such as from Bettermaker. The settings and values ​​are mostly similar.

Brick wall limiters

What is a brick wall limiter?

The Brickwall Limiter opens up Play it safe when it comes to exceeding levels. This guarantees namely NO levels above the specified threshold. Through a delay line analyzed the Brickwall Limiter the incoming signal, before he spends it and then regulates this down accordingly. Because of this delay in the reproduction of the signal the Brickwall Limiter is more suitable in the studio than in the live area. The risk that the musicians will lose themselves due to the delay is simply too great.

A limiter is an important tool in audio editing of music. Especially when the song should reach a certain loudness as possible, there is no getting around regulating level peaks.

Threshold

With most limiters it is possible to regulate the threshold. Of the Threshold defines the specific value to which the signal should be regulated down. In mastering, for example, this is set up -0,4 db (fs) a. This prevents that after the Conversion from 32 bit to 16 bit and then there may still be no peaks above 3 in mp0 and thus cut off because it in the digital domain (fs) nothing above 0 db gives.

Attack

The attack time (start time) indicates when the limiter should start working, or how much signal can go unfiltered into the limiter before it starts to regulate down. Too short an attack time can destroy the transients (first impulses of audio signals), so it can happen that the cymbal, snare or hi-hat no longer occurs powerful in the mix sound. Too long an attack time can result in the incoming signal sounding too sharp or even leading to digital overs (clipping). Therefore, the attack time should be set carefully and rely on your hearing. A a good initial value is in the range of 5-20 ms.

Release

The release time for the limiter indicates when the limiter should stop working. I can't make a recommendation here, as the release time always varies from song to song and from genre to genre. For electronic music with rapid level jumps that happen constantly over a longer period of time, a medium to long release time is more likely to be chosen. Coarser The starting point here is approx. 200 ms. For slower titles that are very dynamic, you can keep the release time of the limiter shorter. Here too, your own hearing is important. Too long a release time often manifests itself in the fact that the song loses pressure and muddy. A release time that is too short is noticeable through so-called pumping. David Guetta is a lover of this method. However, not in the sense of mastering, but rather within individual sequences in the mix.

Knee or soft knee

This function is rarely installed and regulates the transition between the signal that is influenced by the limiter and the original signal. By modifying the Knees, a piece of the sound can be reproduced true to the original. A setting recommendation is to be made at your own discretion.

Possible uses of the limiter

The Limiter or Brickwall Limiter is used wherever there is a deliberate need to limit. This can be the case with live performances, in individual tracks in the sequencer, in the sum on a group track within the mix or in the sum channel of the Master sum for mastering. A limiter should always be used with care. It changes the dynamics and thus also the overall sound. Loud doesn't always sound better! If the limiter is set too hard, the signal can be clipped and larger dropouts occur. In addition, if the limiting is too hard, unwanted resonance frequencies are often brought out again, which are not really important in the actual mix. It is therefore important to work properly in the mix beforehand so that there are no problems with the limiter afterwards. In other words, the limiter can be a good way to monitor weak points or Resonance frequencies in the mix to be identified.