Active Crossover. The LD Systems X223 is a stereo 2 way / mono 3 way crossover in standard 19''/1U rack format. Its rugged construction, high quality and robust knobs as well as the integrated power unit are rarities in this price range. It provides a mono sub output, an adjustable crossover frequency for each channel, adjustable LF/HF and input gains, phase reverse controls, switchable 40 Hz High-Pass filters and symmetrical XLR In- and Outputs. With the LD Systems X223 you get a crossover fulfilling the professional standards and offering great quality and sound characteristics.