I need to know how to set the phase and crossover frequency on the ep 125 sub. I have a sub cable running from the receiver to the sub input.

Joe, if your receiver has adjustable crossovers, it should be set to 80hz(it may have a fixed crossover at 80-100hz). This takes care of all the crossover duties(speakers should be set "small" on the receiver, of course)and the EP125 crossover should be turned up all the way to get it out of the way of the receiver cross.

On phase, if the sub is located relatively close to the mains(right in the corner closest to the speakers is nearly always the best location)the 0 phase setting will probably give the best bass. Of course, try 180 to see if that gives stronger bass.