If multiband compression makes your head spin, you’re not alone. Mastering the art of using a classic, single-band compressor is hard enough. Bake a half a dozen of them into a single plugin, and it’s no wonder so many mixers have no clue how to use multiband compression properly!
Here’s the definitive guide to using multiband compression in the mixing process. For information about how to use multiband compression in mastering, I recommend checking out Ian Shepard’s “How to Master with Multiband Compression” course.
What Is Multiband Compression?
A multiband compressor allows you to split a track into different frequency ranges (called “bands”) and compress them independently.
You can choose to compress only a certain part of a track’s frequency spectrum, or apply different flavors of compression to several areas of the spectrum.
Why might this be useful? Well, I’m glad you asked…
Why Should I Use Multiband Compression?
Imagine you’re mixing a track with a poorly-recorded vocal (not too hard to imagine, eh?). During the recording, the singer was swaying back and forth in front of the microphone. Here’s an example of what this might sound like:
Notice that the vocal sounds fine in certain spots, but excessively boomy in others (“in the orb,” “light,” “down”). So what do you do?
You could try to tame the excessive low end with EQ, but this will change the sound of the entire performance. Here’s the vocal track above, with a 7 dB cut at 170 Hz:
The words that were too boomy (“in the orb,” “light,” “down”) certainly sound better, but the parts of the performance that were fine to begin with (“a face of,” “smiling”) now sound too thin.
You could try automating an EQ – cutting low end only where it’s needed. But this would take ages. And your client just texted you, asking if he can swing by in an hour to listen to the mix…
The solution is multiband compression. Set it up properly, and it will reduce the low end of the vocal when it’s too boomy, but leave it alone when it sounds fine. Here’s our vocal with multiband compression applied:
The words that were boomy are now better balanced, and the other parts of the performance sound great too. Problem solved.
When Should I Use Multiband Compression?
When deciding whether or not to use a multiband compressor, ask yourself the following question:
Am I trying to fix a problem that’s consistent (it doesn’t change over the course of the song) or dynamic (it changes from note to note)?
If the problem is consistent, EQ will work just fine. If the problem is dynamic, a multiband compressor is often a better tool for the job.
Some mixers like using multiband compression on their mix bus. I think this is a bad move, because splitting up a mix into various frequencies and processing them independently can create more problems than it solves (see “What Are The Downsides Of Using Multiband Compression?” below).
Multiband compression is best used to solve problems on individual tracks. I use it rarely – perhaps in only 1 out of 10 mixes. When I do, it’s typically on vocals, but I’ll occasionally use it on other tracks as well. Maybe an acoustic guitar is too boomy, but only on certain notes. Maybe a drum overhead is too edgy, but only when the drummer hits a certain cymbal. Got an inconsistent problem that’s too difficult to fix with automation? Multiband compression can offer a great solution.
How Do I Use A Multiband Compressor?
- Start With One Band:
- If you’re using a plugin with a fixed number of bands (like Waves’ C4), bypass everything except one band.
- If your plugin opens with no bands active (like FabFilter’s Pro-MB), add one band.
- Adjust The Crossover Points:
- Solo the band while the track is playing.
- Adjust the crossover points to isolate the problem you want to fix. The band should be wide enough to contain the entire problem, but narrow enough to exclude the good-sounding frequencies around it.
- Adjust The Threshold:
- Un-solo the band.
- Adjust the threshold so that the band starts compressing when the problem gets too loud.
- Tweak To Taste:
- Adjust the range and ratio controls until the problem is adequately controlled.
- You may need to tweak the attack and release times to get the compressor to react appropriately to the dynamics of the track.
What Are The Downsides Of Using Multiband Compression?
A multiband compressor must pass your track through several filters to split it into different frequency bands. These filters can often add undesirable ringing, distortion, and noise to a track. Even linear-phase filters can alter the sound in an unflattering way.
Processing a track’s frequency bands independently can also alter its natural harmonic structure. This can make many instruments sound disjointed and unnatural – particularly those that were recorded acoustically.
For these reasons, multiband compression works best as a specialty tool. Reach for it sparingly, and listen closely for artifacts.
Hopefully this article has given you a solid understanding of how to mix with multiband compression. If you’re looking for more information, I highly recommend watching the videos below. Both feature vocals, but the concepts and techniques covered can be applied to a variety of different tracks.