Multiband Compression Explained
Published · updated · by Loopin
Multiband splits the signal into frequency bands and compresses each separately. It solves exactly two problems well, and gets used for about twenty.
What it is for
A normal compressor reacts to the whole signal, so a loud kick pulls down the vocal with it. Multiband lets the low band respond to the kick without touching the band the vocal lives in.
That is the entire benefit: independence. Everything else people use it for is better done with EQ.
Problem one: bass pumping the whole mix
If a loud bass note ducks everything else on every beat, a low band with a 3:1 ratio and 1–2 dB of reduction below about 120 Hz fixes it without touching the rest of the record.
Set the crossover at 100–120 Hz, attack around 20 ms, release around 150 ms. If you need more than 2 dB there, the mix has a bass level problem and this is a plaster.
Problem two: harshness that comes and goes
A record that is fine in the verse and painful in the chorus around 3–5 kHz needs something dynamic. A band from roughly 2 to 6 kHz with 1–2 dB of reduction catches the loud moments and leaves the quiet ones alone.
A static EQ cut would dull the verse to fix the chorus. This is the case where multiband genuinely beats EQ.
Why it usually is not the answer
If the problem is constant, use EQ — it is simpler, has no time-domain artefacts, and does not shift the phase relationships between bands. Multiband applied to a constant problem makes the record sound processed for no gain.
And multiband on a master cannot fix a balance problem between instruments, because the instruments overlap in frequency. Pulling 3 kHz down affects the vocal, the snare and the cymbals together.
How to check you have not made it worse
Bypass and match the level. Multiband almost always sounds better simply because it is louder, and unmatched comparison is how people talk themselves into four bands of unnecessary processing.
Then listen to a quiet section. If it sounds different from before, your thresholds are catching material that was never the problem. Compare against a straightforward master at matched level before adding bands.
Frequently asked questions
When should you use multiband compression?
Two cases: a bass that ducks the whole mix on every beat, and harshness around 3-5 kHz that appears only in loud sections. If the problem is constant, use EQ instead.
What crossover points work for multiband on a master?
Around 100-120 Hz for the low band, and roughly 2-6 kHz for a harshness band. Keep reduction to 1-2 dB; needing more means the mix has a balance problem.
Is multiband better than EQ for mastering?
Only for problems that change over time. For anything constant, EQ is simpler, has no time-domain artefacts, and does not shift phase between bands.