Re: Speakers
Ahmed, I don't think you have any "electro-mechanical" problems.
Some factory speakers, those that come with a car have small, cheap filters attached to the speaker that allow for better sound and longer life. Whether they be low pass or high pass filters, you will often see resistors and capacitors next to (and soldered onto) the speaker terminal. These are cheap fixes by the car manufacturer, and in the case that the speaker sounds bad, you should replace your speaker.
A replacement speaker is usually of a higher grade than that of a factory one, and you will be pleased with the sound even without any filters attached. But for the best sound it is best to have a filter network.
Google car audio.
Since you're on here you should know a thing or two about resistors and capacitors, so you also might want to Google filters, butterworth, Linkwitz, Riley, Chebyschev, etc...