What Does a Limiter Do in Audio Production?

Many tools and effects are available when producing music and audio. Not only does a flawless mix require that considerable time and effort be invested, but there’s always more work to be done, especially in the mastering phase.

Whether you're an audio engineer, a music producer, or just starting out in this line of work, you need to know what you're doing when adding effects like the limiter, or you can end up causing more harm than good. But what does a limiter do? We'll go over all you need to know about the limiter and its features, as it’s one of the most powerful tools in the industry.

What Is a Limiter?

A limiter is a type of high-ratio compressor commonly applied during the mastering stage of production. Basically, it’s a signal-processing tool that uses dynamic range compression. That is, when it receives an input signal, it evaluates the volume and lowers the waveform peaks if they reach and surpass a certain threshold value.

Limiter tools are accessible in both software and hardware formats. Most DAWs provide software limiters in the form of VST plugins that work with digital signals. The hardware units, also known as analog limiters, are commonly found in radio stations and professional music studios.

Audio Compressor vs. Limiter

Unlike audio compressors, which focus on compressing individual tracks in the mix, limiters set a ceiling for the output level, and no sound can go above it. A limiter prevents crossing above that threshold, whereas a compressor is used after that barrier is crossed. The compression form is determined by parameters such as release, attack, and knee, as well as how gradually or abruptly the change is made.

Essentially, limiters are all sub-types of compressors, but not all compressors are limiters.

Common Types of Limiters

While all limiters function similarly, some limiters, such as single-band limiters or multi-band limiters, differ in the extent of freedom they provide in a music studio. A frequency band is a specific range, or bandwidth of frequencies within the full range. Depending on your preferences, settings, and hardware, these bands can be smaller or larger. Below are the most common limiter types used in audio production:

Multi-Band Limiters

As the name implies, a multi-band limiter can limit several frequency bands, allowing better control over an individual mix, as well as more precision. Its three bands are typically classified as low, medium, and high.

The three bands have their sound limiters, allowing you to control the dynamic range compression for each of them. Even if you use identical settings for each band, the result is still better and more precise than with a single-band limiter since they are compressed independently.

Any frequency difficulties should be resolved during the mixing stage. A multi-band limiter can work its magic if one frequency range demands more compression and work than another.

Full-Band / Single-Band Limiters

Full-band limiters are designed for use on a full mix of studio recordings, as they work by processing the entire signal. This is sufficient for many situations where a sound limiter needs to be applied. 

Therefore, limiting is not divided into several frequency bands, as is the case with multi-band limiters, but is applied to the entire track. This is how most limiters work, and when people talk about limiters in general, it's assumed that they're talking about single-band limiters.

Full-band limiters are excellent for fine-tuning final sound levels and establishing a proper threshold, but be careful not to drain the dynamics from your audio when using this type.

True Peak Limiters

A true peak limiter works in situations where the analog to digital converter in our equipment is what’s causing the clipping. Some like it, some don’t, but true peak limiters should be used whenever you want to ensure that no clipping occurs when audio is processed through the D/A converter.

Brick Wall Limiters

Limiters with really high ratios are commonly referred to as brick wall limiters. These limiters act as a "brick wall," obstructing any sound that exceeds the preset threshold.

Limiter Settings and Features

To reap the full benefits of an audio limiter, you should first understand its specific functions, as well as how they interact with one another. Although this is a standard tool in audio engineering, you don't have to be a pro to get the hang of it.

The settings on a limiter are similar to those of a compressor. Threshold, Attack, Release, and Gain are four knobs you’ll usually find on every limiter.

Threshold / Ceiling

The threshold, also known as the output ceiling, establishes the level beyond which the signal cannot go, and is often set to 0 dBFS (decibels full scale). The recommendation is to start with a somewhat high limiter threshold and gradually adjust it until the dynamics are reduced to your liking. The limiter will only be engaged when the sound surpasses that threshold.

Release

The release control is one of the most important limiter components. The release knob controls how long the limiter limits a specific sound. A release that's too long creates an unpleasant pumping sound, while a short release may cause an inconsistent listening experience and startle the listener. 

Attack 

The attack function determines how quickly the limiter responds to the audio input signals and limits those signals. Some volume limiters have an attack that affects how rapidly an audio input is impacted by the audio effect, similar to those of a compressor.

Input Gain

Input gain is the amount of signal that is fed through a limiter. The higher the input gain, the higher the endpoint audio; however, please keep in mind that louder isn't always better. Extreme volume levels can cause unpleasant clipping, which can quickly push loud sounds into distortion and damage a mix.

Makeup Gain / Output Gain

A limiter’s settings for mastering and mixing also include makeup gain, which is an overall increase in volume after compression. Basically, it raises the compressed signal's peaks to the same volume level as the pre-compression peaks, maintaining the same peak level and increasing the overall volume. The output gain function can provide a similar effect.

Knee

Sometimes, an audio limiter may feature a knee that lets you control the harshness or subtlety of the limiting that’s being applied. This is less typical, though, because limiters are meant to completely cut off signals above the output ceiling in tracks.

Soft Clipping vs. Hard Clipping

Clipping occurs when the waveform is cut off, resulting in sound distortion. It can damage the drivers in your speakers, the amplifiers, and other components if it's really severe. For instance, limiters are occasionally used when matching speakers and amplifiers in order to safeguard the devices.

Clipping is sometimes applied on purpose, such as with distortion guitar pedals or when overdriving an amplifier tube. Limiters use clipping to prevent unintentional peaking and its negative effects.

A limiter accomplishes this through hard clipping, which generates sharper waveforms similar to a plateau, or soft clipping that has rounded edges and is less noticeable.

When to Use a Limiter?

Here are a few examples of situations where a limiter might be suitable. 

Increasing the Audio Volume While Mastering

When we’re applying a limiter effect, we’re not necessarily increasing the volume. In fact, we frequently soften the sound by ensuring that the volume does not exceed the threshold. 

The makeup or output gain is what really makes things loud. Compression merely creates the necessary volume stability for loudness. That’s why limiting is an excellent tool for making tracks appear louder and more aggressive while avoiding clipping.

On Master, Vocal, and Drum Buses

Audio limiters are typically applied on a master bus to process the entire mix. Tracks are provided with that final volume boost before being exported.

The dynamic ranges of vocal and drum buses can vary quite a bit. Due to its high ratio, a limiter can easily flatten the power of lead vocals, so it’s more commonly used on group vocal buses. However, limiters can come in handy if you need to reduce the peaks on drum buses.

Final Tips

To get the most out of your audio limiter compressor, be sure to keep in mind the following:

• Ensure you're not losing bass frequencies, as limiters have a greater impact on low-end signals.
• Limiting will probably distort high-end signals more quickly, so that’s something you should also keep an ear out for.
• Start with the factory default presets, as you would with other plugins, and customize to your liking.
• Avoid using limiters on individual tracks, as that will surely lead to sound distortion. Limiters are intended for a large group of tracks or the master bus.

Bottom Line

When it comes to audio production, it's all about balance and practice, for both software and analog limiters. In most situations, there isn't a right or wrong way to do things, so experimenting with sound is a terrific approach that’ll get you far.

Practice will help you figure out which limiters you prefer and how they can affect the overall sound of your tracks. The more limiter and compression tools you use, the more your hearing will get used to its subtleties, and you'll eventually learn when and how to apply them.