What Does A Limiter Do In Audio? (How It Works, Single vs Multi)

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  • You may have seen the term used, but what does a limiter actually do?
  • How is limiting related to compression?
  • What are the best settings for Spotify and other platforms?

The Pro Limiter in Pro Tools (Image: Avid.com)

The mastering process is challenging enough on its own, and that’s assuming your mixdown is good to go in the first place.

Once your song is mixed, it needs to be brought up to the optimum level in terms of volume and loudness. Streaming services are very strict about the dynamic range of your audio. Very careful attention to detail must be paid with volume adjustments, but adjusting the gain itself will only get so far before the audio goes into the red and clips.

Instead, we need a special tool for these adjustments, and this is where limiters really help.

You may have a vague idea about how limiters work, or maybe you are familiar with compression but are unsure how limiters are different (and we have a whole article about this, too).

Luckily though, with the help provided below, you should be able to take full advantage of everything that a limiter brings to the table while avoiding some of the most common mistakes that can ruin a mix. We’ll look at the science of compression, why it matters, and what controls are available to you to shape the dynamics of your song.

Ready to get right into it?

What Does a Limiter Do to Audio Signals?

Simply put, a limiter is a type of compressor, and many standard compressors will also function as a limiter. Limiting is a strict type of compression that does not allow the audio to go beyond the threshold. Because of this, limiters let us go loud without clipping. They are often the final stage in the mastering chain, setting the final level and ensuring there are no rogue peaks or spikes eating up the headroom.

This is opposed to a regular compressor which will allow audio to go beyond the threshold according to the ratio. But with a limiter, the ratio is fixed to a high rate such as 8:1 or above. Limiters will often have fast attack and release times as to sound transparent – avoiding the “pumping” artifacts often associated with regular compression.

(If you’re getting confused by these terms, it might be a good idea to back up and have a read of Understanding Compression (Audio Compression For Dummies))

The strict nature of the type of compression found in limiters has spawned the term “brick wall limiting”. This is both a reference to the limiter’s ability to stop the signal in its tracks as well as the appearance of the compressed waveform, which resembles a wall.

As you may expect, not all limiters are created equal. Some are designed specifically for mastering, some work better on drums, and some are prized for their characteristic tone rather than their actual ability to compress audio accurately.

So choosing the right one for you is going to be a bit of a challenge. While conventional logic suggests you should try a few out first, this isn’t always possible with expensive software, and the demos might not be functional enough to help you decide anyway. Plus there are just so many options it’s hard to know where to begin.

Thankfully, you can use our guide to make an informed decision. We’re going to look at everything limiters can and can’t do, what their controls are, and how to make the most of them when it comes to mixing and mastering.

What Controls Does A Limiter Have?

For a full rundown on what each control does and how it affects the signal, I’d suggest you check out Understanding Compression (Audio Compression For Dummies) first. But we’ll still list the ones you’ll encounter and give a brief summary of what they do.

  • Threshold / Ceiling – This is essentially the “level” of limiting and the signal won’t go beyond this point.
  • Input gain – Boost the signal before it hits the threshold. This control is usually only found on limiters with a fixed threshold.
  • Output / Makeup – This is used to add gain after limiting. Your limiter may automatically apply gain compensation, which means the volume increases as you lower the threshold.
  • Attack / Release – These let you change how quickly the gain reduction reacts. Typically you want very short times for limiting. Many limiters will leave these settings fixed “under the hood” so you may not see these controls.
  • Ratio – You will almost never see this on a limiter either, the ratio is often fixed to a high setting and you can’t change it. But if you’re using a standard compressor plugin as a limiter, you’ll want to set the ratio to at least 8:1.

How To Set A Limiter For Mastering

Full Band vs Multi-Band Limiting

You’ve probably heard of the term “multi-band compression” before, or know about multiband compressors. So it’s no surprise that you can find multiband limiters as well. This effect has become quite popular over the last 10 years, with many people discussing “OTT” (or Over The Top) multiband compression that brings out every sonic detail in your audio.

It’s an exciting effect that always yields interesting results as all sorts of hidden grit and dirt is brought to the foreground. But multi-band limiting isn’t just used for special effects – it can also be a tool to help you subtly balance the dynamics of each band.

Let’s look at the differences between full (single) band limiting and multi-band limiting.

Full Band / Single Band

So, if band is shorthand for “frequency band”, in the case of a full band limiter, we are dealing with the entire range of frequencies that can be heard. This is how most limiters operate, and if someone is talking about a limiter in general terms, it’s expected that they are talking about full band limiters.

In fact, most effects are “single-band” unless otherwise specified. Just know that if you see this term, it’s referring to a “normal” limiter as opposed to a multiband one.

Full band compressors are great for final level adjustments and setting an appropriate ceiling (i.e. making sure your final master does not exceed -1 dB). But they can throw your mix out of whack as the change in volume alters how the levels in your mix are perceived.

D16 Frontier is a great free “full band” limiter VST plugin.

In my experience, I can tell if I have pushed the limiting too far when my snares and hi-hats become too loud. Due to their rich frequency content, the change in volume becomes especially apparent as we are so sensitive to higher frequencies. Heavy limiting pushes them to the same level as the kick, which is not good.

With multi-band limiting, however, this is less of a problem…

Multiband Limiting

If you want better control over how the limiting affects the tone of your audio, you are going to want to reach for a multiband limiter.

Simply put, a multiband limiter splits the audio into different frequency ranges and compresses each one separately before summing them all together again.

This is usually the same 3 bands: low, mid, and high. Each of these bands has its own limiter, allowing you to adjust the dynamic range compression individually for each group. Even if you use the same settings for each band, they are still being compressed separately, so the effect is still much richer than a single-band limiter.

If you’re comfortable playing around with an equalizer the odds are pretty good that you’re going to be comfortable with a multiband limiter, too. There is a lot of crossover between the two effects for obvious reasons, but they cannot be used interchangeably.

Multiband limiting sounds great on a drum bus, or drum loops where you are otherwise unable to change the volume of the different drums individually (like with a classic breakbeat).

They are also used in mastering chains to add some “beef”. In this case, you will find them placed before the final (full-band) limiter, which is more surgical in terms of setting the overall ceiling of the rendered waveform.

When Should I Be Using a Limiter?

There are many scenarios where using a limiter is ideal. Let’s look at some…

Making final level adjustments before rendering

This is exactly what we looked at moments ago – using a limiter as the final effect in your mastering chain to set a “ceiling” for your final audio. If you’re applying no makeup or output gain, then the threshold becomes the ceiling.

It’s a good idea to aim for -1 dB, particularly because when music is transcoded (i.e. converted to MP3 or another lossy format) it is possible for clipping to occur in the conversion process. If you’re making EDM or club music, I wouldn’t suggest going any lower than -1 dB assuming you are mastering with the recommended loudness for Spotify and other streaming services (more on this later).

Making things sound louder

This is related to the previous scenario, except loudness is a bit more complicated than pure volume or levels. Really, loudness refers to the consistency of the volume.

A sound that is mostly soft but momentarily loud cannot be considered loud as a whole. But a sound that is consistently loud rightfully is loud.

This might give you a hint about how limiting and dynamic range compression in general works. When we use a limiter, we are not necessarily making things louder. In fact, very often we are making things softer, by ensuring the volume can not go beyond the threshold.

Really it is the makeup or output gain that makes things properly loud. Compression simply creates the right consistency in volume which is necessary for loudness.

Ok, so you can take a sound that is equally loud and quiet and then turn it up so that even the quiet parts are loud without the help of a limiter. But then you run out of headroom and the loudest parts will start to clip. So we need to accept that even without a limiter, there’s still a very real limit to how loud our sounds can be in a digital space.

So, with this in mind, limiting is awesome for making things sound aggressive and in-your-face without the risk of clipping. However, this process is a tradeoff between loudness and dynamic range, so if you’re running your whole track through a limiter, be aware that you can easily ruin your mix if you’re not careful.

Adding color and character

This is especially true for vintage hardware limiters and analog modeling VSTs that add a bit of extra “mojo” to the sound. If this is what you’re after, there’s no need to push the limiter too hard here. These units often add subtle harmonic enhancement and may apply some degree of saturation to achieve this.

Before comparing, balance the volume so that when you turn the limiter off, the audio is just as loud as it is with it on. This will help you make the right call on how the tone color is being affected. While this is a good rule for comparing any effect, it’s particularly relevent here as limiters dramatically affect the volume.

Limiters, Loudness, and LUFS

It’s critically important that you keep a close eye (or ear) on loudness and how it changes the way your music is heard on various streaming platforms and video services like YouTube. We use LUFS or Loudness Units Full Scale to measure the overall loudness and dynamics of audio, and there are a number of plugins you can find that will do this for you.

LUFS is a scale used by Spotify and other services to ensure the music uploaded to their platforms is of consistent quality in terms of loudness and dynamics.

If you submit a mix that is pushing the limiter too hard, you can expect the volume will be ducked by the streaming platform. This stops it from sticking out like a sore thumb when played next to something with more conservative use of compression and limiting.

This used to be a bigger problem, and it resulted in the loudness war of the 90s and 00s (though it is technically still being fought). In short, record companies were using limiters to squeeze audio within an inch of its life, resulting in master recordings that sounded stale and noisy.

So why would they want to do this? Because when we compare two sounds, we instinctively favor the louder one. These loud singles and albums would supposedly outsell their competition based on this idea alone.

So, if you want your music to end up on Spotify, check out their guidelines for mastering for their service. Of course, these rules will vary from platform to platform, but you will be able to find this crucial information easily enough regardless. If you’re not careful, your music will be flat out rejected which, to say the least, really sucks.

In Summary

So we’ve learned a few key things about limiting. Firstly, limiters are a type of compressor. They affect the dynamic range of our audio and help us to make strict and surgical mixing decisions. Without limiters, it would be very hard to get our music sounding balanced on various platforms and streaming services.

But limiters can also have a dark side – they can completely drain the dynamics from your audio and make it sound flat and lifeless. It may sound fun when you’re doing it simply because it’s nice and loud, but this is just a trick your ears are playing on you. While limiters can make things sound loud in a good way, you need to make sure you don’t go too far here or you’ll end up ruining your mix.

So, like so many things when it comes to production and making music, it’s all about balance. The best thing you can do is get your hands dirty and find the limiters that work best for what you’re trying to do. You will most likely end up with a few different types that you use for different purposes.

(For a more detailed breakdown on the differences between limiters and compressors, check out Compression vs Limiting: What’s The Difference?)