Multiband Compression
Compressing different frequency bands independently for precise tonal control in mastering and mixing.
What It Is
A multiband compressor splits the audio signal into separate frequency bands — typically three to five — and applies independent compression to each band. This allows you to control the dynamics of the low end without affecting the highs, tame harsh upper midrange without dulling the warmth below, or add sustain to the top end without pumping the bass. It’s a precision tool that combines the functions of EQ and compression, making it essential in mastering where you no longer have access to individual tracks.
How It’s Done
The signal is divided at crossover points into discrete frequency bands. Each band gets its own compressor with independent threshold, ratio, attack, release, and gain controls. Common band divisions: sub-bass (below 100Hz) for controlling boomy low end, low-mids (100-500Hz) for managing muddiness and boxiness, midrange (500Hz-2kHz) for handling vocal and instrument body, upper-mids (2-8kHz) for taming harshness and sibilance, and air (8kHz and above) for controlling brightness and presence. The crossover frequencies determine where one band ends and the next begins, and their placement critically affects the sound.
Where You’ll Hear It
Multiband compression is a staple of modern mastering, used on virtually every commercially released record to achieve tonal balance and dynamic consistency across the frequency spectrum. It’s also used in mixing on complex sources like full drum buses, vocal chains, and bass guitars that have uneven frequency content. Broadcast audio processing relies heavily on multiband compression to maintain consistent loudness and tonal balance across varying program material.
For Engineers
Use sparingly — multiband compression can quickly make things sound over-processed and lifeless if overdone. The more bands you use, the more potential for artifacts and unnatural behavior. Start with three bands and only add more if needed. Set crossover points carefully — poor placement causes audible artifacts at the crossover frequencies, especially during transients. Use gentle ratios (2:1 to 3:1) and moderate gain reduction (2-4dB per band maximum). It’s almost always better to fix frequency-specific dynamic problems in the mix rather than trying to rescue them with multiband compression in mastering. When you do use it in mastering, A/B frequently with bypass to ensure you’re genuinely improving the master and not just making it different.