Behringer Ultracurve Pro DEQ2496
This unit is a customizeable graphic equalizer, as well as a floating-point digital signal processer. Mark uses a pair of these at the top of his monitor rig to provide a slight delay for the sound coming out of his monitors, so that their sound meets the sound from his speaker cabinets at the same time. Since he has twelve feet between his monitors and his cabs at every show, he can set the delay and not have to worry about phase cancellation.