Learning Audio Mastering Through Presets

Part 1: Multiband Compression

Tips & Tutorials  | 

This blog has been edited from its original format; some references have been changed to reflect Ozone 7.

Although there are many definitions of what “mastering” is, for the purpose of this article we refer to “mastering” as the process of taking a mix and preparing it for distribution.

As part of the mastering process, an engineer corrects any mix balance issues and enhances particular sonic characteristics. The tools used to make these adjustments, such as Equalization (EQ) and Compression, are specialized, complex, and challenging to master.

Many software mastering tools come with presets. While presets on their own will generally not be the perfect setting for every mix, there are other ways that presets can be useful in your process. Studying presets made by professional mastering engineers can be an incredibly useful way to understand more about the mastering process, and how to use the tools to help shape your own sound.

Presets can be useful for feature discovery, inspiring a creative starting point, or even as the final settings for the audio being mastered, should a happy good sounding accident occur. iZotope’s Ozone features a wide array of presets for mastering different genres of music as well as treatment for particular issues and individual instruments.

This is the first in a three part series of blog posts taking a look at some specific mastering techniques as demonstrated by some Ozone presets, and dissecting the settings being used.

Be sure to also read Part 2: Mid/Side Processing and Part 3: Using an Equalizer.

 

Multiband Compression

This is a dubstep-style remix. When mastering in this genre, one of the goals is to restrict the dynamic range and increase presence, while retaining the punch of the kick and snare. This genre tends to be bass heavy, with a lot of low frequency energy to rattle and shake the dancefloor.

The challenge is that this low frequency energy can trigger a regular compressor to react very harshly, also compressing the high frequencies and resulting in a very squashed and pumpy sound that no longer sounds good.

In order to keep a full, punchy low end, the “Drum&Bass and Breaks Master - Basic” preset has been loaded in Ozone.

This preset works, because it uses a technique called multiband compression. Multiband compression splits the frequency spectrum into different bands, such as low, mid and high, and applies different compression settings in each of those bands. Thus, the kick and the snare are still loud, and the exciting synth lines aren’t buried.

Listen to the audio example below with no processing, then compare it against the “Drum&Bass and Breaks Master - Basic” preset.

What can be learned about multiband compression from this preset?

Using heavier compression ratios on higher frequency bands can make the sound brighter and more immediate. Significantly reducing the loud peaks, in just the high end allows more makeup gain to be added, increasing the overall volume of the highs, as seen on bands 3 and 4.

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Compression thresholds may be set very differently on different frequency bands. In this example, there is far more energy and volume in band 2 than in bands 3 or 4, so the threshold setting is more gentle. Not only does this help prevent a squashed, over-compressed sound, but it illustrates why multiband compression can sometimes be more precise and useful than a single band compressor. 

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To sculpt a crisper, punchier sound, this preset uses different Attack and Release times for the high frequencies vs. the low frequencies.. This is because lower frequencies require more time for their transient information to pass through the compressor before compression actually begins. Here, as a result, the attack and release times are set shorter in bands 3 and 4 than they are in band 2.

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The low end doesn’t need much compression. Compressing the highs leaves enough headroom to simply turn up the low end, as seen here in band 1. Because the kick drum sits in this low frequency band, it isn’t being heavily processed, and remains punchy and focused as a result.

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To transparently compresses the signal without harming the attack transients, this preset uses the RMS detection mode.

PRO TIP: Ozone's Gain Reduction Trace overlays a graphic that illustrates the volume adjustments of the compressor onto the waveform. This helps set the Attack and Release times, as it’s possible to observe if the signal recovers in time for the next transient. If it doesn’t, it is likely to sound pumpy.
PRO TIP: The Learn feature listens to the frequency balance and automatically places the crossover points where they will be most transparent. 

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