the seem's like the bass, is a bit less, alot less, in my four 15" mains, and as i said, it seem's the lfe does not funtion unless both main and sub's, are selected, yet im running more test's, hooking speaker's to another amp.'listen, make sure havn't fryed any crossover's in them, i hope i havn't damaged a crossover in rx. receiver lower end, everything else is great, way powerfull, excet 15" bass spk. when i do select both main and sub's, then i have bass, but probably just from sub's, i don't want to have to get another amp.in it's day, it was around 1,500, and still in presteen condition, the whole system is, thank's again