SPL PQ

The SPL PQ is a plugin emulation of SPL’s PQ Mastering Equalizer, a fully parametric five-band stereo EQ built on SPL’s 120V rail technology. The hardware’s main distinguishing feature is per-band switching between Constant Q and Proportional Q modes — Constant Q maintains the same bandwidth regardless of the amount of boost or cut, while Proportional Q narrows the bandwidth as gain increases. Having that choice independently per band gives you more surgical control over how each adjustment interacts with the surrounding frequencies. The plugin version, developed by Brainworx, is officially approved by SPL.

Each of the five bands can be activated or bypassed independently, and a quarter-gain switch reduces the boost/cut range from +/-20 dB down to +/-5 dB for the fine corrections typical in mastering. The plugin adds Brainworx’s TMT component variance modeling across 72 channels, M/S processing, mono-maker, stereo width, THD, and an Auto Listen mode that solos the affected band while you adjust — a useful monitoring shortcut when you’re trying to find problem frequencies quickly.