Let me say first, very nice speakers! Looks like they claim down to 40 hz which is very respectable. I'd say 80 hz a great starting point. I think I read somewhere that one octave up from a speaker's F3 (80 hz for you) is s'posed to be the "correct" crossover point for a system, but there's a lot of "YMMV" in there too.\n\n\nThanks! Their low end is clean, but definitely in need of extension because they drop off very quickly on songs with big bass. I'll start at 80 and work from there.