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User Guide - Studio Mastering EQ

Mastering EQ

Harrison’s fastest, most precise, and most transparent EQ for finalizing your mixes

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 The Mastering EQ has been specifically designed for mastering your mixes and is a must-have for pro audio engineers and enthusiasts alike! The Mastering EQ features a revolutionary filter shape that was originally developed for precise speaker management. This means that the resulting curves are perfect for making broad, musical changes to the final tone while maintaining the harmonic balance between the elements of your mix. Unlike ordinary EQs, when two adjacent bands are adjusted the resulting curve is flat across the band edges, rather than having discrete peaks and valleys. This causes less change in your instrument and vocal character, while applying the desired tonal balance to your mix. Managing a powerful full-range EQ has never been so fast and easy!  


Six Features:

  • Ultra-fidelity equalizer based on Harrison's XTool plugins for digital consoles
  • 31 control bands, high pass filter, low pass filter, level trim, and momentary bypass controls.
  • Harrison’s iconic Filters
  • Innovative DSP curve-match allows a "flat top" across adjacent bands.
  • RTA Analyzer “Graph” Mode
  • RTA Analyzer “Lightning” Mode

 Ultra-fidelity equalizer 

Harrisons Mastering EQ is a high-fidelity equalizer that gives you the sound and feel of Harrison’s XTool plugins for digital consoles. The XTool plugins are renowned for their sonic quality and versatility, and the Mastering EQ brings you the same level of excellence. The Mastering EQ lets you shape your mix with precision and ease, using a variety of features and modes that can help you achieve your sonic goals. The Mastering EQ is based on Harrison’s XTool plugins, which are trusted by professional engineers around the world.



EQ Graph

The center frequencies for each of the 31 band controls are labeled across the top and bottom rulers of the EQ Graph display. Hovering over one of the band control areas will highlight it. Click anywhere within a band control area and drag up or down to adjust the gain of that band. You can also do this by scrolling the mouse wheel. You can adjust multiple bands easily by clicking and dragging horizontally across the EQ display, allowing you to draw the desired EQ curve.

Right-click over a band to reset its gain to 0 (this also works with dragging across multiple bands).

Hold shift while dragging the mouse over bands to smooth any unwanted bumps between adjacent curves.

In addition to the band center frequencies displayed across the EQ Graph, there are also vertical rulers to the left and right of the display that show the gain values corresponding to the EQ and the RTA display.

The ruler on the left is the EQ Range. It displays the gain values corresponding to the vertical positions of the bands.

The ruler on the right is the RTA Range. It displays the levels corresponding to RTA readings and will be disabled unless the RTA is on. Refer to the RTA section of the manual for more information on this ruler and its functionality.


Zooming & Panning

The EQ graph can be vertically zoomed or panned up and down as necessary. By default, the zoom is focused on a gain range of +/-4 (as shown by the EQ Range ruler on the left). If you drag a band past the focused range, the graph will automatically adjust its zoom to include the band’s gain within the focused range (up to +/-14). You can manually adjust the zoom by right-clicking the EQ Range and dragging it up or down.

In addition to zooming in and out, the graph’s Y axis can also be panned vertically by left-clicking the EQ Range and dragging it up or down.

You can reset the zoom and pan back to default by double-clicking or Alt-clicking the EQ Range ruler. 



Harrison is renowned for its hi and low pass filters and the Mastering EQ is no exception.  Mastering EQ has gentle yet powerful high-pass and low-pass filters that can help you refine the sound of your mix. The filters can help you cut out any unwanted low-end rumble or high-end hiss from your mix, and make it sound more crisp and clean. You can choose between 6dB/oct and 12dB/oct for the slope of the filters, depending on how gently or sharply you want to roll off the frequencies beyond the cutoff point. You can also fine-tune the frequency of the filters using the sliders above and below the curve. The high-pass and low-pass filters are one of the many features that make Harrisons Mastering EQ stand out from other EQs.


The High-Pass Filter

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(HPF) controls are located in the bottom-left corner of the plugin window. Enable or disable the High-Pass Filter by toggling the HPF button.

The Low-Pass Filter

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(LPF) controls are located in the top-right corner of the plugin window. Enable or disable the Low-Pass Filter by toggling the LPF button.

Use the sliders to adjust the corner frequencies of the filters.

The dropdown menus select the slope of each filter between 6dB/octave and 12dB/octave.


Output Trim

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The Trim slider in the top-left corner of the window adjusts the trim of the EQ’s output level from -20dB to +20dB.





DSP curve-match

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Mastering EQ features an innovative DSP curve-match technology that allows you to create a flat top across adjacent bands. This means you can boost or cut multiple bands without creating any unwanted bumps or dips in the frequency response. You can achieve a smooth and natural sound with the DSP curve-match, and avoid any phase issues or artifacts that might occur with other EQs. The DSP curve-match is a unique and powerful feature that can help you master your mix with precision and ease



The RTA (real-time analyzer) offers a visual representation of the spectral characteristics of the audio signal being processed. The RTA display is calculated using a Discrete Fourier Transform, which provides high resolution data even in lower frequency ranges.

The RTA button toggles the RTA on and off. 

The Post button sets the input signal to the RTA from Pre-EQ to Post-EQ when toggled on. If you want the RTA measurements to be affected by your EQ adjustments, you should enable this option.

The Decay knob controls how long RTA measurements are displayed before they ramp back down to zero. If the RTA display is changing too rapidly to be useful, you should increase the Decay value. Likewise, if the display appears to be “frozen”, try decreasing the Decay as this might be the result of an excessively high Decay value.

The Length knob is only available in Scroll mode and essentially controls the scroll speed of the spectrum data. If the display is scrolling too quickly or if you would like to see more of the spectrum’s history, you should increase the Length value.

The Type dropdown menu selects between the 3 modes of operation:  Graph, Scroll, and Lightning.


RTA Analyzer “Graph” Mode

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The “Graph” Mode lets you see the frequency spectrum of your mix with 1/10 octave precision. Unlike other RTA analyzers that use FFT-based bands, the Mastering EQ uses equally spaced bands that give you unparalleled accuracy in the low frequencies. You can use the “Graph” Mode to spot any problems or imbalances in your mix and adjust them. The “Graph” Mode is a tool that can help you master your mix with confidence and ease.


RTA Analyzer “Scroll” Mode

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In Scroll mode, the RTA is displayed as a vertically-scrolling spectrogram, providing you with additional time to recognize and target certain spectral characteristics of the audio signal.


RTA Analyzer “Lightning” Mode 

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Mastering EQ features a “Lightning” mode that gives you a unique and innovative way to visualize the frequency spectrum of your mix. The curve shows you the average level of each band, while bright flashes indicate the location of transient peaks in the signal. You can use the “Lightning” mode to spot any frequency spikes or imbalances in your mix, and adjust them with the Mastering EQ. The “Lightning” mode is a cutting-edge and exciting feature that can help you master your mix with a high degree of accuracy.


RTA Trim


The Trim of the RTA’s input signal can be adjusted on all RTA types by clicking the ruler to the right of the display and dragging it up or down. This can be used to increase or decrease the RTA’s sensitivity to the signal being fed to it.

When the RTA is in Scroll mode, the ruler will display the levels of brightness that correspond to each intensity value along the vertical axis. The levels of brightness displayed on the ruler will change accordingly when the Trim is adjusted.  

In Graph and Lightning modes, the scale of the vertical axis can be zoomed by right-clicking the ruler and dragging up or down. 

The RTA Trim / Zoom can be reset to their default states by Alt-clicking or double-clicking this ruler. 


Control Behaviors & Shortcuts

Various mouse & keyboard shortcuts can be used to perform certain actions on the following controls:

Graph Rulers

Action Shortcut
Reset Pan & Zoom or Trim



Fine adjust Pan or Trim

Shift + Left-click & drag

Control + Left-click & drag (Windows only)

Command + Left-click & drag (OSX only) 

Fine adjust Zoom

Shift + Right-click & drag

Control + Right-click & drag (Windows only)

Command + Right-click & drag (OSX only)

Adjust Pan Scroll mouse wheel
Adjust Zoom Shift + Scroll mouse wheel


Combo Boxes (Drop-down menus)

Action Shortcut
Reset to default Alt-click
Scroll through menu items without opening menu Scroll mouse wheel
Select next/previous item (menu must already be open) Keyboard arrows
Close menu (if open) ESC


Action Shortcut
Reset to default Alt-click
Fine adjust

Shift-click & drag

Control-click & drag (Windows only)

Command-click & drag (OSX only)

Adjust value Scroll mouse wheel
Close editor (discarding changes) ESC
Close editor (submitting changes) Enter



Action Shortcut
Reset to default



Fine adjust

Shift-click & drag

Control-click & drag

Command-click & drag (OSX only)

Adjust value Scroll mouse wheel


Additional Features


At the top-right corner of the plugin window are the Momentary Byass and Settings buttons.

Momentary Bypass

The Momentary Bypass button bypasses the plugin for as long as it's held. This is useful for auditioning A/B comparisons quickly. 



The Settings button reveals a pop-up menu where the window size and theme can be adjusted. It also contains a link to the plugin manual and version info at the bottom.


System Requirements

Your system must meet the following requirements in order to run Harrison plugins:

  • Windows 7 or higher
  • Mac OS 10.9 or higher
  • Linux GCC 5 compatible systems
  • OpenGL 3.2 or higher
  • libcurl-gnutls on Linux

macOS M1/ARM Support: This plug-in is provided as a universal binary for macOS and features native M1 support.

Note for Pro Tools users: Pro Tools 11 or higher is required on Mac, 10.3.5 or higher is required on Windows.

Additional requirements on Windows

Harrison plugins require 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.

Note for Linux Users

If you’re experiencing issues with the plugin’s graphics or the GUI isn’t showing up correctly on Linux, make sure your system’s graphics driver supports the minimum required OpenGL version of 3.2 or higher. To check this, run glxinfo | grep Max in a terminal window and make sure that the value listed for the OpenGL core profile version string is at least 3.2 or greater.


If your core profile version meets this requirement but you are still experiencing graphics issues like the ones mentioned above, it is likely that your system is reporting an OpenGL version lower than 3.2 to ensure backwards compatibility with deprecated OpenGL functions. To work around this, you can force the system to report an OpenGL version of 3.2 or higher by setting this environment variable: MESA_GL_VERSION_OVERRIDE=3.2


You can use this as a prefix when opening your DAW from a terminal command like so:


MESA_GL_VERSION_OVERRIDE=3.2 {command_to_launch_program}


Installation & Licensing

Licensing on macOS & Windows

This plugin is licensed through iLok on macOS and Windows. Visit iLok, Licensing and Activation for guidance on activating your Harrison plug-in. 

Licensing on Linux

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

In DEMO mode, after using the plugin for a certain amount of time, it will display a message:

This message will come up periodically unless a license is provided. You can purchase a license directly from Harrison’s web store or from an authorized plugin reseller. Once you’ve purchased a license, install it by entering your license key into the designated field on this screen. Continue to the next section for detailed instructions on how to obtain your license key. 

Obtaining your License Key

After you purchase a license, you will receive a license key that will look something like this:

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

This license key is required to install your license and activate the full version of the plugin. The way to obtain your license key varies depending on where you purchased the license from.

If you purchased the license from Harrison’s web store, you will receive an email with a link to download a text file containing your license key. If you purchased the license from a reseller, you will receive an email containing the license key text.


Licensing your Plugin

When prompted by the plugin, copy and paste your license key into the designated text input field. This will automatically install your license and register it with the plugin.

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:

  • Linux: /home/{your username}

You may keep a copy of this file for your own use. The license is a per-user license and you may install the license file on all of your computers. 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 new computer’s HOME folder. 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.

The plugin will automatically detect your license key as long as the license file is stored in the HOME folder of the computer you are using. After transferring the license file to a new computer, it may be necessary to close and re-open your DAW in order for the plugin to detect the license.

If you don’t want to keep your license in your HOME folder for whatever reason, you may also store it in the following alternative location:  ~/.config/harrisonconsoles

Finding the plugin in your DAW 

DAW operations vary tremendously. Generally speaking, to use the 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 installer will place the plugins in the default locations.

For VST format, on Windows, it is normally expected that the user defines the location of VST plugins, and tells the workstation where to find the plugins. The default location for VST plugins is C:\Program Files\Steinberg\VST.  The 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.


Thank you for purchasing 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.

These 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!