Subwoofer Crossover Setting with B&W 805S

Sorry, but nobody can possibly answer this. Bass is so dependent on the room. Where the bass rolls off with the 805's in your room will be very different than in another room. Then, where you place the sub in that room will make a huge difference as well. So, this question can't be answered. You just have to experiment to find what you think works best.

Thanks all. Always good to get confirmation.

Buy a Lyngdorf RP-1 and let it tell you what you should be doing, based on the acoustics of your room.

I had the 805s with a REL T1 subwoofer. I tried different crossover settings and in the end stuck with 80Hz. There is a reason that this is the default with THX and many processors. It is low enough that the bass is non-directional, and high enough to cover the bass region where most speakers are lacking. If you want to tweak then tweak away, otherwise leave it at 80Hz. You'll probably end up doing that anyway.