When I bought the car I didnt have a head unit. I bought a JVC head unit and the amps wont turn on, the front bottom door speakers dont play and only the tweeters sound OK.

Question is mabey my wires arent spliced properly? I had a friend do it that has installed alot of these at his job(best buy)
Or is it that my amps and speakers are broke or the wires are bad?

I dont know to much about car audio stuff and would like to fix/mabey upgrade my mach 460 system so I can hear it in my loud car .