check the splitter, it should tell u which output has less signal going out of it, if they're all equal, i'd use a 2 way splitter first and let the modem get 1 line off that. then use splitters on the other line to go to the tvs. my parent's house had issues with the cable modem and hd cable box cuz of the way the splitters were arranged (7 tvs + modem). had to rewire it so the 2 strongest signals went to those 2 devices.