Nakamichi Sub/head Unit Acting Up

[jb904]

recently purchased my 98 lexus ls400 with the nakamichi set up (completely stock). just the other day while turning the bass up my subwoofer went out. the next day the subwoofer was going in and out (should have left it alone) but being the curious one i messed with the bass knob again and the same thing happened. unfortunately now i get no bass from the subwoofer. not sure if its a bad wiring connection/bad amp etc etc....any suggestions on whats wrong or any way for me to troubleshoot the problem??? Now for the head unit....all of the knobs ie: volume/treble/mids/fader and etc. seem to work fine except that there seems to some kind of delay when turning them higher or lower. for instance i turned the volume all the way down then to about halfway up and there was like 2 seconds between time before the volume actually "caught up." everything works but im just curious as to why the delay happens and if there is any way to fix it....thanks for any input....