Quad Lim: Multiband Limiter Plugin by IK Multimedia

Quad Lim applies limiting only to the parts of the spectrum that exceed their threshold. Because each band is handled separately, a loud low end or a harsh upper range can be controlled without pulling down the whole mix.

The filter slope control sets how broad or sharp the band division is. Gentler slopes give smoother, wider dynamics control, while steeper slopes keep the bands more separate.

The developer describes the crossover filters as transparent, with an emphasis on avoiding audible artifacts at the band edges.

Time constants and makeup gain are user definable, which lets you match the band limiters to the material. Setting the gain structure of the band limiters carefully is the key to reaching higher loudness without distortion.

An optional master brickwall limiter follows the multiband stage. It is designed so the output cannot exceed 0 dBFS, regardless of how the band gains are set, which makes it useful as a final safety stage.