FabFilter Pro-Q 4—A Mix Real-World Review

New York, NY (February 19, 2025)—FabFilter, based out of Amsterdam, the Netherlands, has released its latest version of the popular Pro-Q plug-in equalizer. Pro-Q 4 has several new features that add to the noteworthy transparent processing of its predecessor, Pro-Q 3, which was released in 2018. These upgrades necessitated a complete redesign to make it the company’s ultimate, mastering-grade mixing/tracking equalizer.

Users of Pro-Q 3 will know that there are up to 24 bands of EQ with selectable filter types and 6 dB to 96 dB/octave slopes including a steep, “brick wall” slope for the high and low-cut sections. For the most precision mastering processing, you may choose fractional slope settings such as 3.3 dB/octave for the LP or HP filter.

An All-Pass filter has been added for correcting phase anomalies, and you can copy-and-paste EQ settings between two or more instances and directly enter settings in the EQ window. Any individual EQ instance can be set to Zero Latency, Natural Phase or the newly improved Linear Phase EQ (with its attendant latency).

There is support for Dolby Atmos 9.1.6, surround channel linking, and per-band, Stereo, Left, Right, Mid or Side modes.

Pro-Q 4 will co-exist with all previous versions of Pro-Q you may have, and FabFilter has re-created and ported its stock Q3 presets over to Q4 versions. The company says Pro-Q 4 will read all previous versions’ presets as long as you use their preset structure and not your DAW’s.

Available for Mac and Windows, Pro-Q 4 comes in VST, VST3, AU, AAX Native, AudioSuite and Clap formats. For Mac, it’s OS 10.13 or higher for 64-bit, while PCs require Windows 11, 10, 8, 7 or Vista and a VST 2 or 3 host.

SPECTRAL DYNAMICS

A significant change is Spectral Dynamics, which builds on Pro-Q 3’s dynamic EQ; it’s available on any EQ band within an instance. Spectral Dynamic EQ will apply threshold-based expansion or compression on a specific EQ band without affecting the rest of the audio running through the plug-in. Essentially, you’re “tuning in” a section of sound on a track you’d like to manipulate—such as dynamically compressing down peaky resonances or expanding upward only the high frequencies of a dark-sounding instrument.

This is a wholly new approach and technique for equalization. Updates here also include: adjustable attack and release times with the given default values a good starting point, and now there is side-chain access. Mousing over a control always reveals a helpful “pop-up” window to explain what that particular control does. Love it!

INSTANCE LIST

Clicking on the track name at the bottom of the GUI launches the Instance List over the main window. Instance List is a brilliant and modern idea when mixing music—especially on large sessions with numerous tracks. It harkens back to the days of mixing on an analog console where all the equalizers were visible in the channel strips in front of you. You can see all the EQ curves you’ve set up and cycle through them to dial in any individual EQ while the mix is playing.

The resizable GUI shows all the individual Pro-Q 4 plug-in instances running at the same time and in one window. You’ll see the spectrum displays and nodes, along with the same editing facilities, only in an expandable, smaller view. The right-hand sidebar shows groups of Pro-Q 4 plug-ins, ready to click on and move to the center of the window for close scrutiny.

Instances come up in a scrollable stack arranged alphabetically, not sequentially. Currently, only VST 3 supports Track Color and Order. In my Pro Tools sessions, I got into the habit of adding a number in front of the track name to order them sequentially. If your drum tracks start at channel 1, you can scroll down to see all the drum channel EQs. Pro Tools has said it will implement Track Order in the next update, with Apple following soon after for Logic Pro.

Using one instance for evaluation, such as the lead vocal, you can see “collisions” depicted in a red haze surrounding a node and band. A collision is a buildup of the same frequencies produced by multiple instances. I found this an excellent tool for mixing midrange tracks—guitars, keyboards, and backing vocals—that often fight with other tracks in the same frequency range.

FabFilter has put a lot of thought into designing this awesome new feature. It’s important for users to learn how to navigate, resize and copy one set of curves from one instance to another. An Auto-Zoom slider enlarges all instances for focusing when modifying them using a complete set of editing controls. You can “Pin” a track or tracks, such as a big collection of backing vocals, for adjustment, and then “Unpin” them back to normal operation. “Jump To” is like a search engine to find a particular instance, or you can always click on an instance in the sidebar list.

I liked how all this works because it is a big time saver in assembling a rough mix on large sessions. I’ve been adapting my Pro Tools workflow to be more efficient using the Instance List. Post-production mixers are going to wonder how they ever got along without this!

EQ SKETCH AND CHARACTER

EQ Sketch is another new feature, one that enables drawing EQ curves. When first inserting a Pro-Q 4 instance on a track, you’ll see a faint “ghost curve” that changes filter shape as you move the cursor across the center baseline.

Starting at 15 Hz, you’ll see a low-cut filter shape. Continuing to move the cursor to the right changes it to a low shelving filter up to 40 Hz; moving through the midrange and higher, it becomes a bell-shaped filter all the way up to 10 kHz, where it becomes a high-cut filter. If you click anywhere, a node is generated, with the curve shape corresponding to the precise location of the node. You can then drag this node up and down at will to build an EQ profile.

A small window pops up over any node and shows controls for +/-gain, Q, bypass, frequency, and a choice of 10 different filter shapes, including All-Pass. There is a larger window at the bottom of the GUI that stays visible whenever a band is selected; it has controls for spectral processing, time constants and a lot more. Again, I look at the pop-up for details, functionality and ideas.

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EQ Sketching speeds the application of an EQ and also works in the Instance List window. Once this rough curve is created, you can start refining its exact frequency, shape, Q and +/- gain. I would add more nodes as needed, and I liked to find “nuggets” in the instrument’s sound energy this way. I like this feature, but wish the ghost curves were a little brighter, bigger and easier to see.

Pro-Q 4 also adds two Character modes to Pro Q’s clean and transparent sound. Two modeled distortion characteristics are available: Subtle is vintage saturation, while Warm is a more saturated, tube-like distortion. Both Character modes are level-and frequency-dependent colors, just like real analog EQs and tube/transformers.

In my testing on a direct bass guitar track, I found these two Characters very subtle, determining they will work better when using them across all instances. Character Mode can be included as your own default, custom preset for use on every track.

IN THE MIX

My first check was to test the Instance List feature by instantiating 77 stereo Pro-Q 4 equalizers across all tracks of a developing mix. I use a Mac Studio with a M2 Ultra, Sequoia 15.2, and Pro Tools Ultimate version 2024.10.1 and had no problem at all launching this big session. It all worked flawlessly.

I liked the resizable GUI windows to help me see deep into the spectrum analyzer window. Sometimes I had issues with setting a node that I didn’t want, but that’s clumsy me. I used the Extra-Large window (100% size) for scrolling all the instances in the mix. Instances seem to be easier to delete or modify in Instance view.

FabFilter Pro-Q 4 is now in my mix template and there is no other EQ that comes close in utility. Its dynamics and spectral functions, along with the Instance List, accomplish the work of multiple processors in an efficient and intuitive way. Highly recommended.