FabFilter Pro-MB online help

Table of contents

Expert band controls

Next to the normal band controls, FabFilter Pro-MB contains additional expert controls, enabled by the Expert button at the right of the floating band controls. These consist of advanced yet highly useful side-chain triggering and stereo-linking options.

Expert band controls

  • The Band/Free buttons select the frequency range of the trigger signal: either the band input signal itself (which is the default setting, used when Expert mode is off), or a freely chosen range anywhere in the spectrum. Enabling Free mode will reveal side-chain filtering controls just above the band controls. It uses intelligent and adaptive filtering, which makes triggering on narrow frequency ranges a lot easier.
  • The In/Ext buttons choose between the internal, normal plug-in input, or the external side chain input. For more information on connecting the external side chain in various hosts, see External side chaining.
  • The Audition button lets you listen to the filtered and stereo-linked signal that will be used to trigger dynamics processing for this band. You can turn Audition mode on or off with a single click, but you can also click-and-hold the button to temporarily audition the trigger signal.

Stereo linking and mid-only/side-only processing

The Stereo Link slider sets the amount of stereo linking for the trigger input signal, and also selects between normal stereo processing or mid-only/side-only processing.

Stereo linking

The first half of the slider range sets stereo linking from 0% (fully unlinked, channels operate independently) up to 100% (fully linked, resulting in the same gain reduction for both channels).

By dragging the slider further, the band will eventually process only the mid-signal (mono content of the processed audio), or only the side-signal (stereo content of the processed audio). Using the small Stereo Link Mode button at the right bottom of the Stereo Link slider, you can toggle between the two.

Mid- or side-only processing can be very useful, especially during mastering. For example, bass or lead vocals are often placed in the center of the stereo image, so only processing the mid-signal will leave all stereo content untouched, ensuring the most transparent end result possible.

To better understand the working of these settings, enable the Audition button. You can now directly hear the effect of stereo linking and mid-only or side-only processing!


  • When triggering on a very specific frequency, choosing a very narrow range in Free mode often works better than the default Band mode.
  • When using mid-only or side-only processing, hold down the Alt key while adjusting the Output Level knob for a band to easily apply make-up gain. For example, when using 100% mid-only processing, holding the Alt key while dragging the band's Output Level to +6 dB, will also set the panning to "-6 dB Side". This ensures the side signal stays unchanged, only adding make-up gain to the mid signal.
  • The Stereo Link slider is of course only enabled in the stereo version of FabFilter Pro-MB.

Next: Processing mode

See Also
Basic band controls
Display and workflow

Table of contents