Got a little bit of a problem with the audio in my car.
i have a 4 channel amp + comp set front. rear speakers are normally off via fader.

so couple of days ago, i noticed the sound in my car were not normal. noticed one side was louder than the other.
moved my fader to the right, sound was fading and dead. tweeter was not as clear as before. softer sound in a way. 2 way speaker was missing it's bass and clarity.

moved the fader all the way to the left, sound is normal as how it should be.

Troubleshooting:
removed right side speaker to the left - sounds normal. speaker not spoil.
moved left speaker to the right and it was not giving me the sound as before.
conclusion - not speaker problem.


i'm thinking maybe amp, head unit or rca or connection or something. how do i know whats wrong or spoilt?
any advice as to what else can i do to troubleshoot. I am not really a tech or expert in ICE so please explain what i need to check and do.

Thanks for any help in advance.