SabrinaX Sub-Crossover

First time posting. I recently got a new pair of SabrinaX speakers and paired them with two Martin Logan 1100x subs. The system together sounds incredible. The SabrinaX is rated down to 31Hz. Where should I cross-over the subs? I did it at 35Hz with a steep roll-off (4th order) but wondering if people with more knowledge have any recommendations? 



Thanks so much for all the great advice! 

I forgot to mention that I am driving them with a McIntosh MA8950. 

They are plus or minus 3 db at 31 hz. Ask Wilson what order the speaker is 

2 nd or 4 th and stick with that   Go around 37-38 hz. You never want overlap 

at least 6 db higher for your specs are not flat at 31 hz try 73 hz kthey 38 

on. A bunch of music , btw the Martin logan subs are not in the same league 

a Svs 4000, or ultra 16 much better controlled ,the JL audio Fathom are the best of the bunch ,sealed are always more accurate then vented or passive radiator .

the ML subs are decent ,I am just speaking in absolute terms.

Thanks audioman!

Unfortunately, my budget is exhausted after the McIntosh and Sabrina's so the subs are a carryover from my prior system. The remaining $$$ is for proper cables. Frankly, the way the room acoustics are optimized when the Wilson dealer was setting the Sabrina's up they were tricked into thinking the subs were on when they weren't. 

The subs crossover should be set at least 10 hz over the lowest frequency rating of the speakers. Mine are set at 13.5 over.

One thing I should have mentioned, is that in-room performance of speakers has almost nothing to do with the specified or quasi-anechoic (Stereophile style) measurements.

Room gain is real, as are room modes which can move the bass output singificantly up or down.  Setting a sub or crossover by published specs is really tough compared to doing it by measurement.