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Harrison Multiband Compressor


What is the Multiband Compressor?

The AVA Multiband Compressor is the latest implementation of Harrison’s renowned Multiband Compression algorithm, as used in ultra high-end post & film facilities worldwide.  Now in the fourth generation, the Harrison Multiband Compression algorithm has been continuously tweaked by our customers in high-end music,  film, broadcast, and video-post production.

Harrison’s reputation for “true analog in the box” sound is due to our unique development heritage, where we first created an analog processor and then converted the processor to digital while retaining the sound and character of the original.  

The results are quintessentially “Harrison”:  effortless, smooth and transparent.


  • Intelligent algorithm requires minimal effort to get excellent results.
  • Band Solo and Auto-Solo features to help dial-in the desired frequency ranges.
  • RTA analyzer display helps to locate problem frequency ranges.
  • Capable of up to 12dB reduction in each band.
  • Sidechain “key” input with dedicated EQ. 
  • Zero-latency processing, suitable for “live” use.
  • “Expand” mode provides an additional creative effect.



The main display graph provides control over the four band frequencies and depths.

Click anywhere inside the bands and start dragging to change frequency and depth of that band. Using the scroll wheel you can adjust just the depth to really dial-in the exact amount you want!

RTA Controls:

The main display also features a high precision, high-speed RTA analyzer (“Spectrum Graph”, or “Scrolling Graph”) , which you can engage to be PRE or POST EQ changes. It also features a Decay knob, which allows you to control the decay rate of the display, and a trim control.  

NOTE:  the RTA requires considerable CPU resources and should be disabled when not in use.

Input Threshold Controls:

The main input meter, and threshold slider (on the left) controls how much material is passed into the plugin (-60dB - 0dB).  Moving the threshold slider down (a lower threshold) will increase the overall compression effect.

In addition to that, each band has its own input meter and threshold to let you have fine-grain control over how much material each band is working on (-15dB to +15dB).

Moving the individual thresholds down (lower threshold) will increase the compression effect for that band.

Band Bypass and Band Solo Controls:

Every band can be bypassed and removed from processing by clicking on its associated ‘IN’ button.

Every band can also be solo’d so you can hear the material the band is working on.

Band Frequency and Band Depth Controls:

The band frequency control controls the low frequency of the band’s bandwidth.  Adjusting a band’s start frequency might affect the width of bands adjacent to it.  The available frequency settings are:

Band 1) 20hz

Band 2) 50 - 400hz

Band 3) 145hz  - 2.5kHz

Band 4) 1kHz - 8kHz

Attack, Release, Knee, and Makeup Gain:

  • Attack (200μs - 20ms)
    • The ‘Attack’ knob controls how long it takes the signal above the threshold to reach full compression.
  • Release (20ms - 200ms)
    • The ‘Release’ knob controls how long it takes the signal, once it falls below the threshold, to return to an uncompressed state.
  • Knee (3dB - 24dB)
    • The ‘knee’ control defines how far the signal must exceed the threshold to achieve full compression.  A smaller knee setting will result in more aggressive compression.
  • Makeup Gain (0dB - 12dB)
    • The ‘Makeup Gain’ control allows you to apply additional gain to the output signal, to ‘make up’ for the attenuation applied by the compression.

Auto Solo:

The ‘Auto Solo’ control allows you to automatically audition the band that you are changing.   This helps you to determine the frequency content of the band, as you adjust the frequency range.


The ‘Expander’ control switches the main operation of the compressor from a Multiband Compressor into a Multiband Expander

In Expander mode,  the gain reduction curve is applied when the signal falls below the band’s threshold. 

Key Input:

The “Ext. Key” control allows you to use a sidechain as the signal driving the compressor.

If Key Input is enabled, then:

  • The main input meter and threshold will be referenced to the KEY (sidechain) input, not the main input.
  • When a band is soloed (using auto-solo) then you will hear the main signal input, not the sidechain.
  • The sidechain EQ is applied to the key input signal.

Sidechain EQ:

The sidechain EQ is a single-band equalizer.  By setting the shape of the band ( high/low-pass filter, bell, or high/low shelf )  you can modify the signal that drives compression in each of the 4 bands.  For example, you can use the filter to remove all high frequencies from the sidechain input, and use only the low-frequency energy to drive the compressor bands.

The “S” (solo) button will send the EQ’d sidechain input to the output for auditioning.

Connecting the External “Key” input

Dynamic effects ( like Compressors, Gates, and Expanders ) measure the volume of an audio channel, and then apply a change (either louder or softer) to the main signal. The signal that is “measured” is called the key signal.  Most commonly, a compressor uses its own input as the key signal.  But some processors allow you to feed a separate signal into the key detector

Each DAW has a different method for connecting a track to the AVA sidechain key input, and each format ( AAX, VST3, AU, and VST2 ) treat the additional sidechain input separately.

It is beyond the scope of this manual to describe each DAW’s method to connect the sidechain input.  Our product demonstration video describes how to make the connections in Mixbus (VST), Studio One (VST3), and ProTools (AAX).

Stereo and Multichannel operation

When used in multichannel mode ( stereo or surround ), dynamic processors must have the ability to apply gain-reduction to all of the channels simultaneously: this prevents the stereo (or sorround) “image” from shifting when one channel is affected differently than the others.

The AVA Mastering Compressor calculates the “maximum” gain reduction that would be applied to any channel, and it applies that amount of reduction to all of the channels in the plugin.

Some hosts allow you to create individual mono instances on a track or bus.  In this case, the gain reduction will not be the same for all the channels in the bus.

Usage Notes

Taming Uneven Frequency Ranges

To address issues like uneven bass notes or harsh sibilance,  you can; and then apply gentle compression to even-out the level of that frequency range.

  • Suggested settings:
    • Use the provided RTA to recognize the problem area, and adjust the band frequencies to encompass the problem area.
    • Set a mimumum threshold (-15) on the problem band.
    • Start with the “knee” setting at max, to apply gentle compression.
    • Attack/Release knobs should be left near the default values.
    • Now lower the master threshold, and/or decrease the “knee” until the desired effect is achieved.

If necessary, you can use an EQ after multiband processing to make-up any lost volume in the affected range.  Or, if you have individual tracks available, it is sometimes better to increase the input level of those troublesome tracks into the multiband processor.

Maximizing Loudness

Multiband processing is an effective tool for maximizing the loudness of a mix.  By compressing each band separately, you can avoid artifacts caused when one frequency range is driving the gain reduction, when other ranges should not be processed so heavily.

  • Suggested settings:
    • Use the provided RTA to recognize the ranges of your song: low bass, low mid, high mid, and high frequency ranges.
    • Adjust the band frequencies to encompass each of the ranges.
    • Attack/Release knobs should be left near the default values.
    • Start with the knee setting at its minimum, to apply hard compression limiting.
    • Now lower the master threshold to achieve the desired amount of compression, and increase the “knee” knob to avoid artifacts, until the desired effect is achieved.

Use the “makeup gain” knob to maximize the volume after the individual bands have been processed.

Artistic Effects (pumping)

Many DAWs provide the ability to feed the sidechain “key” input from a different track source.  For example,  in electronic dance music it is common to compress the synth and/or bass track from the kick-drum.  This creates a tempo-synced breathing sound that swells before each beat.  This is a useful mixing technique for any dance-music style.

If you are working with drum loops without a separate kick track, you can use the sidechain EQ to focus the effect on the desired instrument.  For example:  to trigger the gain reduction on the kick drum, you can low-pass-filter the key signal so only the bass drum is triggering gain reduction.

By adjusting the depth and threshold of each band, you can cause useful effects:  like compressing only the lowest register of the bass, when the kick drum sounds.

Note:  when you are using an external key,  the same signal is sent to all 4 bands (the key is not filtered into 4 separate bands).  This allows you to focus the key signal on a range (like bass) but affect a different range ( like mids or highs ).

Increase the “release” knob until the effect accentuates the pulse of the song.

Enabling the Expander mode will create the inverse effect:  you can gate the keys or bass to sound during the kick drum, and get quieter between notes.  This can result in a more stocatto sound.

Extra features of the Harrison series plugins:

The “ear” icon engages the momentary-bypass function, which allows you to audition the un-affected signal while you hold the mouse button; then restores the settings when you release the button.

The “gear” icon launches a menu with additional features including resizing, theme selection, and plugin version number.

The alternative “Vintage” theme uses the color scheme of Harrison’s large-format console software.

The plugin “Pain-free demo”:

When you install Harrison’s AVA plugins, you are provided a “pain-free demo” of unlimited length.  You may continue to use the demo for as long as necessary to determine if the plugins meet your expectations.

We do not:

  • Annoy you with a popup authorization message, every time you start your DAW.
  • Install anything to your system outside of the plugin ( AU, AAX, VST ) folder.
  • Prevent the plugin from saving or loading its state.

In demo mode, the control panel will become disabled after a short period of operation.  Then you can re-initialize the plugin’s control panel by clicking anywhere in the dialog.  This is the only limitation. The plugin’s effect will continue normally, allowing you to evaluate the sound of the plugin on your session.  You may still adjust the plugin’s controls in your DAW’s “Generic plugin UI”, from a control surface, or via automation.

The AVA plugins will fully save and recall their state, even without a license. This avoids embarrassing situations that arise with plugins who don’t remember their state in demo mode.

If you send a session to a collaborator, they are not required to purchase an AVA license to hear the plugin’s effect. They may simply download the demo to install the plugins, and the plugins will operate normally. This allows you to share your sessions with other engineers, and have confidence that the mix will sound as intended. If they want to make changes to the plugin settings then they should buy a license for their personal use.

We believe this policy eliminates many of the compromising features of plugin demos, while providing a strong incentive for regular users to purchase the plugins.

This product includes software developed by the OpenSSL Project for use in the OpenSSL Toolkit (

Purchasing and Installing your plug-in license:

In DEMO mode: after about 30 seconds of use, the plugin will display a message:

NOTE:  You may click the red “X” to dispel the license dialog for further evaluation.

To permanently enable the control panel, please purchase a license from an AVA plugin reseller, or purchase directly from Harrison’s web store.  The license is a per-user license and you may install the license file on all of your computers.  The license file has your name encrypted in it, so you should not share it with other people.  Your name will appear on the top of the plugin’s control panel to indicate that it is licensed to you.

Automatic Installation:

The plugin can help you download and install the file to the correct location.  This is the preferred installation method if you already have the plugin’s license window displayed.  Please see the next 2 pages for instructions.

Installing a license from Harrison’s online store:

Buying from Harrison’s online store:   Click “Buy Here” to visit Harrison’s online store and purchase a license.  If you purchase from Harrison’s store, you will receive an email with a link that looks like this:

Right-click the link and select “Copy Link Location”.  Then right-click in the white box, and select “Paste”.  The plugin should report that the license was downloaded and installed.  If you receive an error message, please contact our plugin support email:

Regardless of the method used,  the result is a license file in your HOME folder;  see the next page for backup & installation instructions.

Installing a license from a reseller:

If you purchase  a license from a reseller, you will receive an email with text that looks like this:

{your  name}*AVA-MC*DC-138971-151520-1|gGLbnvCZJe386ULohzfQN6cIsoZ71n7c+AUg==|

Select the bold text, and copy/paste it into the plugin’s text field, like this:


Regardless of the method used,  the result is a license file that is saved to your HOME folder;  see the next page for backup & installation instructions.

License file backup & installation:

Once installed, Harrison’s license files are simple text ( .txt ) files which are stored in the user’s HOME folder(*).  The HOME folder is the folder that contains your Desktop, Downloads and other folders.  The location of your HOME folder is different for each operating system:

  • Mac OSX:     /Users/{your username} 
  • Windows:    C:/Users/{your username}
  • Linux:   /home/{your username}

You may keep a copy of this file for your own use.  To install the file on a new computer, simply save the file to a USB key or other transferable disk;  then transfer the license file to the target computer’s HOME folder.  The license file has your name encrypted in it, so you should not share it with other people. 

Alternative locations:

If you would like to install the license to a hidden location, you may store it to an alternative path:

  • Mac OSX:  ~/Library/Application Support/harrisonconsoles
  • Windows:   ~/AppData/Local/harrisonconsoles
  • Linux:  ~/.config/harrisonconsoles

For additional questions about the license, please contact our plugin support department via email:

Finding the AVA plugin in your DAW :

DAW operations vary tremendously.  Generally speaking, to use the AVA plugin you must follow these steps:

  1. Install the plugins, using the provided plugin installer application.
  2. Follow your DAW’s instructions to “scan” for new plugins.

Please refer to your DAW manual to see which plugin formats ( AAX, AU, VST, or VST3 ) are supported by your workstation.

Most plugin formats require that plugins are installed to a specific location on the system.  In these cases, the AVA installer will place the plugins in the default locations.

For VST format, on Windows, it is normally expected that the user define the location of VST plugins, and tell the workstation where to find the plugins. The default location for VST plugins is C:\Program Files\Steinberg\VST.  The AVA plugin installer will save the VST (.dll) files to that location if a custom VST path is not provided by the OS.  If you are having trouble, you should verify that the path is included in your DAW VST scan paths.

Additional requirements on Windows:

The AVA plugin requires the “Windows C++ Universal Runtime” to be installed on your computer.  Universal runtime is part of the system’s core libraries on Windows 10. On Windows versions Vista to 8.1,  it will be automatically installed via Windows Update. It is also possible to install the runtime manually, but that is outside the scope of this manual.

Thanks for your purchase of this Harrison plugin!

Harrison has been making products for the audio engineering industry since 1975.   We continue to make these products, with intense dedication, from our Nashville, Tennessee, factory.  

As the audio industry has changed through the decades, Harrison has too.  Originally launched to provide mixing consoles for music recording studios, the Harrison brand has extended to provide products for live broadcast, live sound, theater installations, post-production, film dubbing stages, and bedroom studios.  We’ve lived through the launch of the commercial music industry; the maturation of analog; the digital revolution; the establishment of the internet; and now the acceptance of computers as the de-facto platform for the audio industry.  In our pursuit of audio excellence, we’ve developed our own analog circuits, digital I/O solutions, digital DSP engines, control surfaces, audio workstations, and nearly every aspect of pro-audio technology.

“If you asked a hundred engineers, mixers and producers to define the “perfect console” you would probably get a hundred answers. The answers, however, would all contain the same salient points.”
“The “perfect console” would have totally transparent sound, capturing the true musical quality of all performances. It would have unlimited features, facilities, and functions. It would perform all required tasks with a minimum of operator effort. It would be totally reliable and require no preventive or corrective maintenance…
You can spend the rest of your life looking for the “perfect console”. You’ll never find it. You will find, however, that we have what you need.”- quote attributed to Dave Harrison;  Harrison MR20 brochure; circa 1982

True-er words were never spoken; indeed every year there are many products and technologies that seem tantalizingly necessary for audio excellence. Our lasting experience has proven that simple, straightforward, well-engineered, and great-sounding tools are the only necessity.

The AVA plugins represent the pinnacle of Harrison’s engineering practices for digital audio sound & workflow.  We sincerely hope that you enjoy using these tools as much as we enjoyed creating them.  Your continued support is greatly appreciated!