The Rane AC 22S Active Crossover is a stereo 2-way with a mono subwoofer option, or it can be used as a mono 3-way. It employs state-variable 4th-order Linkwitz-Riley filter alignments to minimize phase difficulties in the critical crossover region.
Simply put, a Linkwitz-Riley alignment is two cascaded 2nd-order Butterworth filters exhibiting identical phase characteristics on their Low pass and High pass Outputs. This characteristic guarantees in-phase outputs at all frequencies. In-phase outputs are mandatory for proper acoustic summing of common signals from adjacent drivers in the crossover region. An added benefit of this topology is steep 24 dB per octave rolloff slopes. A slope of this magnitude guarantees drivers designed to produce a specific range of frequencies, and no more, will not be driven past their limits, thereby minimizing distortion and driver fatigue.
To further guarantee the transparent operation, adjustable Delay circuits appear on the Low (& Mid when used in 3-way mode) Outputs of each channel to compensate for any physical misalignment of the drivers. Time correction ensures the mechanical phase alignment of adjacent drivers will be acoustically correct, thus maintaining the integrity of the electrical phase alignment of the crossover