I agree with a 50-60hz starting point. But in addition to the phase switch the problem with Rel is the phase is either 0 or 180 degrees. The problem there is if the sub is leading or lagging the main speakers flipping the switch then they will only will then be lagging or leading the mains (opposite of the starting point). So what you have to do is either move the sub closer to farther from where you start. The most I ever had to move my B3 is 4". Once you get the phasing right it will be easier to set the crossover point and the gain. I start with the gain high when trying to determine the phasing.
Good luck and have fun
BTW once it's dialed in you should not be able to hear where the sub is located and the monitors will have a full range sound.
Good luck and have fun
BTW once it's dialed in you should not be able to hear where the sub is located and the monitors will have a full range sound.