distortion problem

[Sabby]

gday people.
well ive got a small problem, im usually good with car stereos but something is playing up
my sub.. or amp.. it distorts at only certain bass hits. other times its fine. ive put in 3 different subs so its something to do with the amp tuning i hope. it even distorts at low volume.
what to do?

[holdenboy]

Model numbers and how its been wired would be good. Without knowing any of this we'll only be stabbing in the dark.