Recently I have purchased a used Mazda 6 (2010). But It has some problem with the sound system. I have noticed that only the rear door speakers are working (front door speakers and the speakers behind the rear passenger seat is not working). I have checked the fade settings and ensured that the rear and front sound is balanced, but still, it is not working.
What would be the possible problem? And how much it will cost to fix? And any suggestion?
I have talked with a car audio repair center, and they suggested changing speakers including an amplifier (They do not even diagnose the problem).