FabFilter Pro-C Review – Modern Compression With Style

By | January 6, 2015

FabFilter is an Amsterdam based plug-in developer company known for their great sounding, innovative and workflow-friendly audio plug-ins. In FabFilter’s own words, they have “never been afraid of reinventing the wheel”.

This is the FabFilter Pro-C review, which is their workhorse compressor plug-in. If you’re on the lookout for a compressor, read on to find out whether FabFilter Pro-C is for you.

Let’s dive in

FabFilter Pro-C

FabFilter Pro-C

At first sight, FabFilter Pro-C strikes me as a very modern-looking compressor plug-in with its clear design and visuals. Everything seems to be laid out in a neat, crisp way.


The Preset Menu

On the top, you can find the Preset menus, which are full of usable presets to get you going as well as an A/B button to switch between two different compression settings.


Hovering the mouse over a function will open a help pop-up

To the right you can find the Help menu, which can be of use if something is unclear about the compressor, or if you just need to learn about some of its functions. Additionally, by hovering the mouse over a knob or function, an interactive help pop-up will appear (which is awesome!)

The compressor is divided into five main sections, which I’ll present to you next.

The Basics

  1. Input Gain, Threshold, Knee Setting, Ratio and Compression Style selection


    Input, Threshold, Knee, Ratio and Style

The Input Gain controls the volume being sent into the compressor. This is useful if the incoming signal is either too quiet or too hot for the compressor to process effectively.

It also includes a pan ring to adjust the panning for the incoming signal (if the Expert mode is on, which is discussed later on in this review).

The Threshold sets the level above which the signal will become compressed. In other words, turning the knob towards the negative values will enable more and more compression.

The Knee buttons switch between Hard Knee and Soft Knee. With Hard Knee compression, the compressor starts working only until the signal passes the set threshold. With Soft Knee, the signal will be compressed gradually as it approaches the set threshold.

The Ratio knob can be thought of as controlling the subtlety or aggressiveness of the compression. With a 1:1 ratio, nothing is compressed. 1.5:1 and 2:1 ratios are subtle, 3:1 and 4:1 are noticeably punchier and 8:1 is already very aggressive compression. Anything above 10:1 can be considered limiting.

The small dots around the Ratio wheel are presets for certain ratios, ranging from 1.10:1 to 10:1. They are useful for browsing through to find a satisfying ratio for your material. 2:1 to 4:1 are usually good ratios for regular track compression.


Compression Styles

The Compression Styles include three options: Clean (allround), Classic (vintage) and Opto (slow).

Clean and Classic are program dependent which means they will act accordingly to the signal you feed through the compressor. The character of the compression and the attack and release times might vary while using these modes.

The advantage of program dependency is the compressor will automatically become more “flexible” when it needs to. For example, when compressing a whole song: during a fast, percussive section of a song the short release which is set to suit the flow will change to a longer release when a slow, gentle breakdown kicks in.

  1. Attack and Release

    Attack and Release

    Attack and Release

The Attack value can be anything between 0.5ms to 500ms, which is a good range to find the optimal attack for the compressor. Basically the fastest attack time is very fast, and the longest half a second long.

The Release values range from 50ms to 5000ms (five seconds). At the fastest setting of 50ms, the recovery time of the release is effective for even the fastest material, such as drums or quick vocals.

Above the Release lies an Auto –button. This changes the behavior of the release to automatic, which is an excellent function in the compressor. It can be set from fast to slow.

The auto release sounds very beautiful and transparent, and is excellent in processing full mixes or instrument groups. Sometimes a fixed release value just won’t work, especially if the source material is very complex.

  1. Output Gain and Dry Mix


Output gain and parallel compression

The Output Gain knob works as the makeup gain of the compressed signal. When compression is applied, the signal gets quieter because of the gain reduction. Use the Output Gain to get the signal back to its original level. As with the Input Gain, the Output knob also features a pan ring, if Expert mode is enabled.

The Dry Mix knob is used for parallel or “New York” compression. How it works is, you introduce some of the original signal back to work together with the compressed signal. This technique is useful if you need to retain the transients of the original signal, which are of course being “squashed” by the compressor.

In practical terms, parallel compression can be used to create punchy and big sounding drums or a tight vocal take. By default, the Dry Mix knob’s gain is set at zero, and only the compressed signal is passing through. Just pull up the gain of the Dry Mix knob and off you go.

The advantage of the Dry Mix knob is parallel compression can be done within the plug-in and no mixer routing is needed to create alternative tracks to become compressed in parallel to the original.

The Dry Mix also has a pan ring around it after Expert mode is enabled. You could use the pan rings of the Output and Dry sections to pan the compressed and uncompressed signals to the opposite sides of the stereo field, to get an interesting stereo image (in left/right mode of course, but I’ll get to these later in the Expert mode controls).

Above the Output Gain is an Auto Gain button. When enabled, it will automatically adjust the makeup gain without any need to touch it. This is a handy and time-saving function for setting up a good compression setting quickly.

But… The Looks!

  1. Visual Aid

The number one thing about Pro-C is the visual section. The compression and the behavior of which can be visualized very effectively. Together with focused listening, the visual cues can be used to your advantage.

The Visuals

The Visuals. Ratio, threshold and knee are on the left, gain reduction is shown as pink graph and yellow meter on the right together with input gain in green.

You can easily see the incoming signal passing the threshold point, the “hardness” of the ratio and knees and the gain reduction. The gain reduction can be observed in two ways, through the scaled digital meter or through time, which is visualized by a transforming graph.

Sometimes I know I don’t want to compress a certain part by more than, say, 3dB. With the visual readings, I can easily make sure I get the compression where I want it to.

The dB scale set to 8dB. Notice also the transparency of the gain reduction graph, which is reduced by a fair amount.

The dB scale set to 8dB. Notice also the transparency of the gain reduction graph, which is reduced by a fair amount.

The gain reduction graph also shows the attack and release curves through time, which is helpful for observing and setting the right attack and release values. You will basically see what you hear.

The digital meter will also show the input gain of your source material, which is nice.

You can set the scale of the gain reduction meter by clicking on the button below with dB values on it. Most of the time, I use the 8dB scale because I rarely do more than 8dB of compression to anything. But if I do, I have the options to choose from 8, 16, 24 and 48dB scales.

As an extra feature, you can tweak the transparencies of the visuals with the three little knobs below in a linear fashion. You could for example turn down the transparency of the gain reduction curve a bit so it’s barely visible, so you’d have to use your listening to judge the compression, but still be able to see the curve if you wish.

Or if you want, you can turn off the visuals completely by clicking the “Power” –button on the bottom left.

The guys over at FabFilter really have thought about everything, which makes Pro-C such a special tool.

Getting Physical

  1. MIDI Learn

    MIDI functions

    MIDI functions

Yes, you can use FabFilter Pro-C physically by using a MIDI controller, such as a knob or slider on your MIDI keyboard. You can assign physical knobs to any function inside the compressor.

All you need to do is enable it by clicking on the “Enabled” button, click the “Learn” button to enable MIDI learning, click a function you want to use (such as Attack or Release) and move a physical MIDI control. That’s it!

For making the MIDI functions work in your DAW, have a look at the Help Topics included in the Pro-C via the Help –menu – should you have any problems with it.

The MIDI functions of the Pro-C have made me use it almost exclusively in compression duties because I can just close my eyes and apply compression just like in the analog world, touching the hardware. Mixing with the eyes is a trap to fall into. I love the fact I can have a physical connection to my sound and shape it by feel by twisting a knob , and not a clumsy mouse.

For the Expert

A sixth section is accessed by clicking the “Expert” –button under the visual section. The Expert mode is not initially visible until enabled.

  1. Side Chain options and Mid/Side Compression

The Expert settings

The Expert settings

The Expert –button will reveal the advanced controls of the Pro-C. By clicking it, you can notice pan rings appear around the Input and Output Gain and the Dry Mix knobs, as I told you earlier.

The controls include Internal/External side chain options, Left/Right or Mid/Side processing, the side chain gain knobs for the two processing modes and a side chain filter on the bottom featuring an Audition –button.

The two gain knobs essentially act as “sub-thresholds” for the left/right or the mid/side channels. The pan rings around them are used to unlink the channels, so the compressor will process them individually.

When both the pan rings are centered, the channels are linked and the compressor will process them equally. If you hold down Shift on your keyboard and pull the left or mid pan ring to the left, the right or side pan ring will move to the opposite direction an equal amount.

At the furthest position, the channels are completely unlinked and will work in either dual-mono or total mid/side control modes. Any other position between the centered and the furthest will provide a mixed value towards linked or unlinked.

Pro-C in unlinked Mid/Side control. Take a look at the yellow gain reduction meter, the mid channel is hitting -7dB whereas the side channel is touching -3dB.

Pro-C in unlinked Mid/Side control. Take a look at the yellow gain reduction meter, the mid channel is hitting -7dB whereas the side channel is touching -3dB.

This might sound complicated, but when you try it yourself on the Pro-C, you’ll get the hang of it.

The digital gain reduction meter will show individual left/right or mid/side gain reduction, when unlinked.

With these advanced controls, you could do tasks such as compressing the left and right channels individually in dual-mono mode, or compress the mid and side channels individually

With mid/side compression, you can essentially compress the mono and stereo components of the mix by setting individual thresholds to both – meaning individual amount of gain reduction to either. Or you could leave either completely untouched.

Bear in mind the attack and release and ratio values stay universal.

Pro-C in mid-only mode. Notice the side channel's gain is set so zero, therefore gain reduction occurs only on the mid channel.

Pro-C in mid-only mode. Notice the side channel’s gain is set so zero, therefore gain reduction occurs only on the mid channel.

Let’s say I have a full mix where the vocal is just a little bit too dynamic and loud. As the vocal lies in the center of the stereo field, also known as the mid, we can only enable compression of the mid component of the stereo signal and therefore make the compressor only process the vocal.

Of course, there are other elements in the middle as well, such as the kick and snare drums and bass. But this is where the filter comes into action. We can isolate the frequency area of the compressor’s side chain so the compressor will only be processing those frequencies – the vocal in this case.

Another case would be if the left side of the mix has a guitar that is too loud compared to the piano on the right side, we could simply enable the dual-mono mode and compress the left channel a bit to tame down the guitar and therefore enhance the balance of the stereo image.

By clicking on the Audition –button below the filter, it lets us hear only the area the filter is affecting. Handy for fine-tuning the filter cut points.

In mastering, the side chain filter is very useful for making sure the kick drum doesn’t make the track pump for triggering the compressor with deep sub energy. Simply by adjusting the high pass filter up to 80Hz we take care of the matter.

With the filter, you could also accomplish some advanced vocal mixing techniques, such as shown here.

Side chain filter

Side chain filter

What does it sound like, then?

Pro-C is a very transparent compressor

Pro-C is a very transparent compressor

FabFilter Pro-C is an incredibly transparent compressor, meaning it doesn’t add any additional coloring or saturation to the sound, unlike some vintage compressor emulations do. But that doesn’t mean Pro-C wouldn’t have vibe.

Of course, sometimes color and character is wanted, but it could be added afterwards with tape saturation and distortion plug-ins.

By experimenting with combinations of the knee settings and the compression styles, you can easily find the type of compression you are after.

By enabling hard knee and the Clean style, you’ll get a really snappy and poppy compression, which could be great for drum kits or kick drums.

A soft knee and the Opto style will give you a gentle but “grabby” compression which would sound great on solo piano and slower pieces of music.

The Classic style with soft knee combined with fast attack and release will give you a fast compression, great for rock drums or fast hip hop vocals. Experiment with the different modes and you’ll find great settings for your music.


Pro-C is a great track compressor to control the dynamics of instruments, vocals and busses. It’s even suitable for mastering as well because of the built-in parallel compression and the dual-mono and mid/side modes, aside from a great, transparent sound which is essential for mastering.

FabFilter Pro-C is a true desert island compressor in my opinion. What I mean by this it’s pretty much the only compressor you’d ever need. It’s easy to use, has high quality and transparent sound and is very intuitive to set up thanks to its great visual components and MIDI controls.

Would you take Pro-C to a deserted island?

Would you take Pro-C to a deserted island?

Sure, I use lots of other compressors too because I like having lots of different sounding compressors in my arsenal. But if I had to make or mix a track using only Pro-C, I’d be happy to.

Pro-C offers anything and everything you would need a compressor to do.

If you’re looking for a clean, transparent compressor with tons of features and functionality and great sound quality, this is it.

If you have any questions about this review or about FabFilter Pro-C, leave a comment below and I’ll be sure to get back to you.


FabFilter Pro-C is available as 64-bit VST, VST3, AU, AAX Native, AudioSuite and RTAS (32-bit only) and is priced at 160€ ($190) including VAT.


  • Great sound quality
  • Clean and transparent compression
  • Deep functionality and customizability
  • Visuals are intuitive and helpful
  • Equally suitable for beginners as it is for experts
  • MIDI functions


  • Expert mode requires a bit of a learning curve

FabFilter Pro-C is available to buy at PluginBoutique.com.
You can’t go wrong with this one, as it’s a keeper in your music production toolbox. Download the trial and see for yourself!

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