3-Way Stero/4-Way Mono Frequency Crossover with Limiters . 24 dB/octave, state-variable Linkwitz-Riley filters for precise frequency separation. Absolutely flat summed amplitude response, zero phase difference. Individual limiter and phase reverse switch per output. Adjustable time delay for phase alignment between drivers. Switchable 25 Hz subsonic filter per input for low-frequency driver protection. “Low Sum” function provides low-level mono output for subwoofer operation . Switchable equalization for constant directivity horns. Shielded toroidal mains transformer for minimal noise interference.