Ending up with a great mix takes quite a bit of time and effort. But even if you’ve managed to beat the odds and you’re happy with how your mix sounds, there’s still work to do. The mastering process, while not necessarily as exhaustive as audio mixing, still requires attention. As we’ve gone over before, mastering is where the song fully comes together, for clarity, loudness, and quality. One of the most powerful tools in this endeavor is the audio limiter.
What is an audio limiter?
An audio limiter acts a lot like an audio compressor, with a few key differences. With compression, you’re focusing on individual tracks in the mix. You compress the kick drum, for instance, to even out the volume, attack, and release of that mix element. The threshold indicates when the compression kicks in, while the ratio determines how much the signal gets reduces after reaching the threshold. Parameters like attack, release, and knee determine the shape of compression, or how gradual or sudden the change occurs.
A limiter takes compression to the extreme and provides more use in the mastering process than during mixing. In fact, a limiter is a type of compressor with a really high ratio. As its name suggests, limiting sets a limit, or ceiling to the output level. In other words, no sound beyond that threshold can get through. So while normal compression begins once a threshold is passed, limiting doesn’t allow that crossing at all. It’s more of a brick wall (the most potent limiters are even called brick wall limiters). This levels the playing field (so to speak) so that the song remains even throughout.
Two types of limiters
Audio limiters, like audio compressors, come in two flavors: full-band and multi-band. Both types follow the same basic principle but offer different degrees of control. Let’s take a look at each kind.
Full-band audio limiters
When we talk about mixing with EQ we often use the term “band.” A frequency band refers to a specific range (or bandwidth) of frequencies within the entire spectrum. These bands can be larger or smaller depending on preference, settings, or the hardware you use. So when we say “full-band,” we’re regarding the frequency spectrum as a whole. In other words, full-band audio limiters don’t really take EQ into account. Limiting isn’t separated into multiple frequency bands but is relegated to the song as a whole.
Multi-band audio limiters
On the other hand, multi-band limiters offer more precision, with several frequency bands at your disposal. So, if a certain frequency stands out too much or needs some love, even after you’re done mixing, a multi-band limiter can provide a fix.
For instance, sometimes while mastering you realize the overall high-end of the song bleeds through too much. You might not have noticed until you began adjusting for loudness. You can always simply mess with EQ at this point, but sometimes using a multi-band audio limiter works even better. By limiting the level of a particular frequency band, you’re making the whole track any louder while balancing everything further. Additionally, that high-end might only pop in at certain points of the song. Rather than using EQ mix automation, a multi-band audio limiter can save you a lot of time and energy.
When to use (and not use) an audio limiter
As previously mentioned, the best time to use an audio limiter is during the mastering process (but not in the mastering channel–rather, the final stage of mastering). Read this for more on how to prepare your track for mastering. However, limiters can also be used for other creative purposes. If you’ve ever wondered why clipping occurs, limiting is sometimes the culprit. When a signal wants to blast past the limiting threshold but can’t, it’s squashed and scrambled down to “fit.” This can result in clipping. While most producers avoid clipping, sometimes it’s used for various sound effects, textures, and other artistic choices. Still, implementing distortion or saturation usually provides a better alternative for this type of sound than forcing clipping.
For tamping down individual mix elements or making them more punchy, use compression and EQ instead. This will allow more dynamic control and ultimately result in a better mix. If you use a limiter while mixing, it can throw off the way you balance mix elements against one another. Always save limiting for the end once you’ve already nailed the mix in front of you.
Audio limiters and mastering: how to use limiters
So, mastering remains the best use for limiters. This occurs after completing the mix. Again, it’s important to note that limiting should not occur on the master channel. Now is the time to take the mix as a whole and adjust its loudness and possibly its frequency profile. If you’re not fully comfortable mastering your tracks on your own, MasteringBOX offers an automated mastering service. Limiting isn’t the only part of mastering, but it’s probably the most important. So when it comes time to master, how do we use an audio limiter?
First, keep in mind the LUFS (loudness units full scale) metering system. If you recall, this system acts as a guideline for the loudness level of commercial music and audio. Different music distributors and streaming services dance around different levels. Right now Spotify’s standard is -14 LUFS and Apple Music’s is -16. Use these standards as a guide for how loud you want your master in the end by increasing your input gain. Depending on how you set recording levels and other factors, you might have to increase input gain by a little or a lot, relatively.
Most limiters, like standard compressors, offer attack/release control as well. So once you’ve landed at a good loudness level, you can adjust attack and release times for the limiter. Remember, a quicker attack results in more aggression. A slower release means a smoother track.
Lastly, pay attention to the output gain of the track as well. Clipping can still occur through certain speakers and devices when the song gets converted for distribution and streaming. To avoid clipping, check to see that the output level doesn’t peak above 0.0 dB.
An audio limiter is a powerful tool, if and when used correctly. Remember that limiting should take place only after you’re done mixing. Otherwise, you risk killing the musicality of your song. You’ll also probably waste more time, in the end, fighting your own mix. You can use a full-band or multi-band audio limiter depending on the needs of your mix. The former adjusts loudness across the frequency spectrum while the latter takes into account different frequency bands. If you want your perfect mix to rest at the perfect loudness level and beam with clarity, be sure to utilize an audio limiter. And again, be sure to use MasteringBOX‘s automated mastering program if you’re still learning how to master yourself!
About the Author
Ethan Keeley is a musician, voiceover talent, and writer from Rochester, New York. When he's not on tour with his band Unwill he's working on new songs and stories.
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