Schwerkraftmaschine Multi-Band Compression Without Frequency Splitting - How It Works

  • 01/05/2017
  • Michael Krusch
  • Story
  • Schwerkraftmaschine
Our Schwerkraftmaschine comes with 11 different compression modes. We'd like to provide a bit of detail on each of them.
Let's start with the Multi-Band Complex mode.

What is Multi-Band Compression

Classic multi-band compression splits the signal into multiple frequency ranges, or bands, that are then compressed separately. This helps the mastering engineer keep a tight rein on the individual frequency bands.

Mastering experts will tell you that it only makes sense to work with individual spectral ranges if you're dealing with at least 5 different frequency bands. Otherwise the frequency bands end up so broad that there's no way to have a targeted impact on the individual zones.
Because multi-band compressors typically include a complete parameter set involving attack, release, threshold, ratio and makeup gain for each channel, it can slow your workflow unnecessarily.

Multi-Band Complex

The Schwerkraftmaschine features a Multi-Band Complex mode. How does it work, given that the Schwerkraftmaschine uses only one control parameter per stereo channel?

Like other compressors, the Schwerkraftmaschine breaks the signal into several frequency bands. This is handled at the digital level, however, through side-chaining. Each of these frequency bands is used to create a separate control signal.

And that is where the commonalities with a multi-brand compressor end.

A custom formula is used to combine the control signals into one joint control signal.
Each frequency range has its own influence on compression, ensuring a balanced compression mix based on psycho-acoustic insights into loudness perception.

This formula is based on the principles of Equal Loudness Contour (https://de.wikipedia.org/wiki/Geh%C3%B6rrichtige_Lautst%C3%A4rke), with in-studio adjustments using listening tests to match the requirements of modern music.



It's well known that the longer wavelengths associated with low frequencies tend to produce distortion on shorter attacks, as the compressor cuts into the wavelength. To counteract this, the timings for the different frequency bands are individually tailored. For example, the Schwerkraftmaschine reacts to lower frequencies with a slower timing than is used for mid-level frequencies.
High frequencies, by contrast, are assigned quicker reactions, as there is little risk of distortions in the attacks.

This approach is not one-size-fits-all; some music is poorly served by this kind of weighting of the individual frequency bands. To accommodate this, you can also change the Tilt EQ on the side-chain filter to adjust the weighting for the individual frequencies for a specific song.

Summary

The Multi-Band Complex mode does not work 100% like a multi-band compressor. By the same token, it also avoids its deficits: non-linearities and phase shifts along the splitting frequencies and a spectral balance for the overall mix that changes based on the signal.
It is also affordable compared with a 5-channel tube audio compressor.

As would be expected for devices with character, there's a certain amount of learning curve involved here.
The parameters are presented very clearly, though, helping dispel fears about multi-band compression.

You may quickly find that Multi-Band Complex is the perfect tool for mixes that just don't sound right under broadband compression.


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