Originally Posted by ontopofm
after subs and amp installed, there is hiss w/ about 1/4 volume turn up, i really do not know if it's coming from sub or amp
Hiss is such noise signal comprising high frequency components, your subs normally are not able to play that noise. I assume you made a wrong grounding. This is the case e.g. the amp is grounded onto the (-) bolt of the battery, thus inducing the low frequency noise from the electric generator into your amp.