I just picked up a used JBL PB12 off craigslist. When I hooked it up there is hardly any sound coming from it. The previous owner had the volume turned way down, almost to 0. I turned up the volume and there was not much low end and the bass got really boomy, and not any deeper. When I have my klipsch ksw-12 hooked up and everything is fine. Plenty of low end bass. However the klipsch is only rated at 105w and the JBL is 250W. I know the JBLs had issues with the amps, so that may be part of the problem. I didnt think that the 105w klipch would beat the 250w JBL as far as sound output goes. As far as settings go the JBLs volume is set around 10 o'clock and the cossover is turned all the way up. I let my denon 1016 handle to crossover. My main speakers are crossed over at 80.