Rel sub x-over fs/click

I'm not sure what you are asking but I can't tell you how hard it is to set up a subwoofer without measuring what's actually happening in the room. 

I did change the rel to a svs sb17 and I would like to have the same crossover settings. But I dont know the x-over fs I had on the rel only that is was around 12 clicks 😀

I have  Rel T9x's, not sure if your sub same setup. In any case my Rel crossover settings go from minimum 30hz to max 120hz, 39 clicks. So, this means aprox. 2.31hz per click.

On my pair of S-812's both the gain and the crossover are set to 10 clicks. Of course, there are many variables to be experimented with.

My REL has a 30 to 100 hz range.  1.8 dB per click.     I have the volume set to 6 clicks from zero and x-over is four clicks from 30 hz.  

Speakers are about 88 dB sens 

REL recommends 10 clicks to start but your main speaker's sens will determine where the volume range will be.   

I set my T/9X RELs according to the bass frequency response of my Wilsons which meant an approx 50 hz setting. The test results posted for the Wilsons seem to show a pretty bumpy bass response where there is a 10db dip at 20 hz but a strong rise to a peak of 50 hz. My gain is very low so it augments here and there but has added to the spatial response in a nice way.