Adding sub to Sonus Faver Guarneri Evolutions...need advice where to set crossover on sub


As the title say, I recently pulled the trigger on a Rel T/5i sub to pair with my Sonus Faber Guarneri Evolution monitors. Ultimately when funds allow again I will add another sub. For now, I only have 1.  I have a small room that is 9x10x9 with the back wall only being 3’ tall, above that the room opens up to my family room and kitchen. I listen at fairly low volumes, no more than 75dbs typically. The Evolution speakers start to roll off at 72hz and its -6db point is 43hz. Its -3db point is around 60hz. Any advice on where set the crossover on the Rel would be appreciated.
128x128tboooe
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.

As you also said first pick 0 or 180 which ever sounds best then move the sub back or bring forward a few inches to get what’s in-between to further get it in phase.

Cheers George

Thanks guys. I am going to have to read up and get a better understanding of phase and how to test for correct phasing.  
@tboooe I just used my ears but will admit I thought I had it right a couple of times.
I followed the setup procedure outlined by REL.  My B1 integrates well with my Auditor Ms.  My phasing is at 0.