Key Filter™ and Key Listen™
Mackie's proprietary Key Filter and Key Listen can be used to trigger Compression or gating based on specific frequencies.
The QUAD Comp/Gate uses an internal bandpass filter, with variable frequency and width, to highlight specific frequencies to trigger compression. This is a great feature for controlling blaring horns or peaking vocals. (see below)
Gating is accomplished by using internal High-Pass Filters (HPF) and Low-Pass Filters (LPF) to isolate signals. As an example, the QUAD Comp/Gate could be set so the kick drum no longer triggers the snare gate. (see below)
The highly innovative Key Listen feature enables the user to monitor, and gdial-in,h the specific frequency range of the triggering content.