I have a 92 Landcruiser with the 9-speaker audio and there is a sub all the way in the back passenger side 6 1/2 inches. There is very low noise to it and hardly pumps anything. The speaker, though, still looks good and not worn out although it may have gotten moist??? Anyway, I thought It was the amp that was going bad so I Changed that with a used on which was working great in the other car I got it from. When I installed the new one, I still get the same results as when I had the old amp on. SO now my last option is to change the 6 1/2 sub... Any suggestions???