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Digirack Plug-Ins & How to Create a Multi-Band Compressor

NOTE: There's also a link to download a Pro Tools session with one already created for
you using RTAS plug-ins so that everyone can open it.

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Waves Linear Phase Multiband compressor
Waves Linear Phase Multiband compressor

Multi-Band Compressor

First off, if you've ever wondered what a Multi-Band compressor is, well here it is, broken down into individual components. Today, I'm going to show you how to create your own using the digi-rack plug-ins that comes with Pro Tools. Although it is easier to open a Multiband compressor plug-in, not every one has one, so were going to do it the old-fashioned way and create one. Most plug-ins these days are just easier ways to do workflows that already exist. The good news is, if you can create your own, you have many more options and flexibility. The example given could very easily be adapted into a 10 band multiband with additional Aux tracks and crossover points.

There's also a link to download a Pro Tools session with one already created for
you using RTAS plug-ins so that everyone can open it.

A Multi-Band compressor is an advanced form of compression that splits your audio into different frequency bands, allowing you to compress each band individually. This is one of the "Secret Weapons" of Mastering engineers for years. When applied to a mix, the Multi-Band compressor has crossover points that can be set to targeted frequency ranges. If a snare drum is too loud in a mix, these points can be set to where the main frequency range of the snare drum is between two points, and can then be compressed or limited, without compressing the bass or treble along with it. Pictured above is the Linear Multiband Multi-Band compressor from Waves. Others makers of Multi-Band compressors include the Waves C4 & Linear, MCDSP’s ML4000 and TC electronics' Master X3.

We are going to create our own Stereo Multi-Band compressor using a few Aux tracks and some of the built in digirack plug-ins that come with Pro Tools. We will start with a 4-Band setup, but after you get the hang of it, you can build a larger one with as many bands as you like.

Stereo Multi-Band Compressor

The cross-over

First, we need to split the audio into individual frequency bands. To accomplish this, we will create 4 stereo Aux Tracks, and set bus 1-2 as input for all 4 Aux tracks. Now any stereo tracks outputs can be set to bus output 1-2 to go through the 4 aux tracks. In this case, we're using a stereo track of a mix that needs to be mastered. Insert the 7-BAND EQ 3 plug-in into Insert A of each of the Aux tracks. Name the Aux tracks as "Aux Low," "Aux LowMid," "Aux HighMid," and "Aux High." Now we are going to use the low-pass and high-pass filters to filter specific frequency ranges to each Aux track as follows:

Set the Q setting for all HPFs and LPFs to 24 dB/ oct as shown above and then set the frequencies as follows:

Aux Low: Set the LPF settings to roll-off everything above 120 Hz.
← Aux LowMid: Set the LPF to 1.5 kHz and the HPF to 120 Hz.
← Aux HighMid: Set the LPF to 5.00 kHz and the HPF to 1.5 kHz.
← Aux High: Set the HPF to 5.00 kHz.

At this point, each Aux track can control a specific frequency range. The outputs of all of the Aux tracks will still be merged together in outputs 1-2. Any plug-in that we insert onto each Aux track will process just the frequency range remaining from the filtering above it. Adding a compressor to the HighMid Aux track will allow you to compress just the frequency range between 1.5 kHz to 5.00 kHz. The idea of this example is to add a compressor after each 7-band EQ, allowing independent compression of each.

Digirack Compressor / Limiter


Now, insert the Compressor/Limiter DYN 3 plug-in right after each of the EQs. You can now set different compression settings for each frequency range if you like. For adding a little more punch, try starting with a slow attack, like say, 30 msec, and a release time of 80-120 msec, ratio to 3.0:1, and bring down the threshold until you get 1-3 dB of gain reduction for mild compression. These settings will allow the transients to pass through, while compressing the tails of the sounds. Try this for each of the 4 bands. After getting these settings in, adjust the Gain setting of each compressor, while watching the meter for the corresponding track until all of the meters are peaking at about the same volume. If you are looking to get the mix a little more under control, you may try setting the compressors with faster attack and release settings, like a 10 us attack and a 5.0 msec release. This will compress the transients more, with less compression on the tails of each sound. Try playing with both to hear the difference between the two. When you get comfortable with the concepts described here, try adding more bands for more control.

If you happen to have other EQs and compressors, try them out as well. My personal favorites are to use a Massenburg MDW 5band EQ, Sonic NoNoise High-res filter, MCDSP NF575, RND Uniquel-izer, or Waves Linear Phase EQ to set the frequency ranges. Then for compression, I like to use the SSL master-bus compressor, Impact, or TL-Aggro followed by a good limiter on each band like the waves L1 or L2, or the RND Finis to catch any peaks that may get through the compressors. Then on the master fader, I like another of my choice limiters to keep the overall mix from peaking. There is no exact set of plug-ins that works for every song, so having a few template sessions with different configurations helps speed up the process. I prefer to "Master" this way vs. using a single Multi-Band compressor, as it has way more flexibility and control. Sometimes I'll create an imager in the HighMid and High frequency bands to push the stereo image wider in the higher ranges without affecting the lower frequencies.

To use the Multi-Band compressor template, download it to your audio drive and import a stereo audio file to master. This will give you a starting point to work from. As you create Multi-Band setups, save them for future uses.

If you like the lesson above, join our Pro Tools courses for a few days at ProMedia Training at any of our 8 locations nationwide, for hands-on Pro Tools Training.

NOTE: There's also a link to download a Pro Tools session with one already created for
you using RTAS plug-ins so that everyone can open it.

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