FabFilter Pro-MB Review

FabFilter steps up to the plate with a new dynamics plug-in – but has it bitten off more than it can chew? Alex Holmes finds out.


Price £139
Contact via website
Minimum system requirements – Windows 7, VST 2/3 host or Pro Tools – Mac OSX 10.5, AU/VST 2/3 host or Pro Tools

As anyone who regularly reads MusicTech.net will know, we’re big fans of FabFilter’s plug-ins, thanks to the slick GUIs and incredibly smooth and well thought-out workflow. The company has already covered EQ, compression, limiting, gating and de-essing in its Pro range, so it seems a logical progression for the next release to combine many of these elements in a multiband dynamics processor.

However, working with multiple bands can prove confusing, and the sheer amount of power it provides can have disastrous results if you don’t know what you’re doing…

A Band Apart
Pro-MB is available in VST, AU and various Pro Tools formats and features up to six bands of compression or expansion. The first thing you notice is that the bands can be placed anywhere in the spectrum, allowing you to focus on specific frequency spots and essentially making Pro-MB more of a dynamic EQ plug-in.

Like FabFilter’s Saturn, you simply hover over where you want to add a band and then click. If two bands are near to each other they will snap together to form a more traditional crossover system, but they can be easily broken apart again by clicking on the unzip icon. You can also control the steepness of each crossover slope and boost or attenuate the band, much like a traditional EQ.


Things get more interesting, though, when you turn to the dynamics controls. Here you’re presented with threshold, range, attack, release, output gain, ratio, knee and lookahead, plus an Expert panel that accesses controls for M/S and sidechain input. Everything links directly to the exquisite main GUI, so it’s easy to see what effect your tweaks are having.

Notably, the input level for each band shows up as a volume meter around the threshold knob, which makes setting the right threshold a breeze, and the amount of gain-reduction is subsequently shown across the middle of the spectrum analyser as a crisp yellow line.

Other key features include a global dry/wet mix dial for parallel processing, up to 4x oversampling, band solo/mute and bypass options, and M/S volume so you can expand or narrow the width of any band. Luckily, context-sensitive help hints appear when you roll over an item, helping you to understand all the various controls.

Just a Phase
The key word for Pro-MB is flexibility, with a large collection of presets showcasing what the plug-in is capable of. Whether you want to use the expander to add some 2kHz transient energy to the middle channel of a drum buss or carve out space by feeding a vocal into the sidechain input on a full-sounding guitar part, it can all be done with speed and precision. The sidechain section also has a Free mode, where you are presented with a frequency slider and can choose a different part of the spectrum to trigger the compression or expansion.

However, one of the most impressive features of the plug-in is the Dynamic Phase processing mode. Given how much damage can potentially be done due to phase shifts in Minimum mode and transient smearing in Linear mode, FabFilter has developed an algorithm that employs dynamic filtering instead of splitting the bands. The result is a more transparent sound that achieves the same frequency response but avoids latency and smearing, and introduces phase changes only when the volume of the bands is changed.

Tool for the Job?
Some may consider £139 to be steep for a single multiband compressor plug-in, but when you consider that you’re also getting a flexible EQ, transient shaper and M/S stereo width controller, it’s a good-value package. Features aside, it’s the fluidity, ease of use and exceptional sound quality that make Pro-MB such a great asset.

The excellent visual feedback combined with the Dynamic Phase mode mean you can make accurate adjustments that sound natural and transparent, whether you’re working on a single instrument channel or mastering an entire track.