FabFilter Pro-MB

Most multiband compressors start with crossovers — you define split points that divide the entire spectrum into regions, then process each region whether you need to or not. FabFilter Pro-MB flips this. You create a band only where you actually want to work, and everything outside it passes through completely unaffected. One band on a low-mid buildup. Another on a harsh high-frequency range. The rest of the signal — untouched, with no crossover colouration, no phase artefacts.

The three processing modes are where Pro-MB becomes technically interesting. Minimum Phase is traditional multiband — no added latency, but the crossover filters introduce permanent phase shift at band boundaries, present even when no compression is happening. Linear Phase eliminates that phase colouration entirely, but introduces latency and pre-ringing — an artefact that appears just before transients due to the non-causal nature of linear-phase filters.

Dynamic Phase is FabFilter's solution to the problem both modes create. The core idea: crossover filtering is only applied at the moment gain is actually changing. When nothing is being compressed or expanded, the signal passes through completely unaltered — no static phase shift, no latency, no pre-ringing. The filters only engage dynamically, and only for as long as they're needed. In practice this makes Dynamic Phase the default choice for most applications: zero latency without the colouration drawbacks of Minimum Phase, and cleaner transient response than Linear Phase.

Each band is fully independent: threshold, ratio, range, variable knee, attack, release, output gain, lookahead up to 20ms, variable stereo linking, mid/side processing, and an external sidechain with the option to trigger on a separate frequency range. Crossover slope is adjustable per side from 6 to 48 dB/oct. Any band can be soloed, muted, or bypassed independently. Up to six bands can run simultaneously.

The global wet/dry runs from 0 to 200%. Beyond 100%, the processed signal is amplified before blending — useful for parallel compression where you want the dynamics effect to punch harder than a standard wet/dry blend allows, particularly with expansion.

Up to 4x linear-phase oversampling is available for reduced aliasing artefacts on demanding material. Latency from oversampling is automatically compensated by the DAW's PDC.

Who Is This For?

Engineers who need precise, surgical multiband control — mastering, stem processing, problem-solving on individual tracks. The Dynamic Phase mode makes it genuinely transparent in a way that traditional multiband processors aren't, and the band-first workflow makes it faster to set up than any crossover-based alternative.