I have the premium alpine stereo system. I'm running a custom amp in the trunk to all the speakers. Each speaker is getting 75 watts RMS at 14.4v. My rear right speaker stopped working last summer so I replaced it with a new used OEM one. Sure enough as soon as I plugged the new used one in, it started working. So I thought I was all done. Up until last week. That new speaker just stopped working too! Now I know that the rear doors have mid and tweeter off the same channel coming from the amp (same wire), and that this whole time the tweeter has continued working. Why does this speaker keep failing while the others are fine? I don't think it could be anything at the amp, since the same wire that comes from the amp also powers the tweeter, and it has been working fine. Any ideas?

 

It could very well be the amp. A leaky capacitor will allow DC to get through to the speaker which will overheat it and let the smoke out.


It won't waffle the tweeter because the tweeter has a capacitor of its own used to block low frequencies (and you can't get lower than DC!).


To check, access the speaker with the stereo on, and place the leads of a VOM set on 20 DC volts across the speaker leads. You should NOT see a steady DC voltage on the speaker terminals. If you do, you;ve found the problem.


If you don't, you may have just experience Murphy's law as applied to replacement speakers...and you simply got a bad one.

 

After testing multiple speakers (including the old speaker I replaced from the door) they all seem to work properly when connected up directly to the amp with different wiring. So I think the problem lies in the wiring going to the midrange in the door. Not sure yet where the problem is along the wire.

 

After more investigation I've discovered that the wires used in my door are the wrong color. The rear right is supposed to be blue/white and blue/yellow but they are green/white red/yellow. The wiring is colored wrong only from the door connector to the door. The wiring in side the car is correct.

 

Finally fixed the problem. Turned out to be melted plastic on the OEM Alpine speaker. When I bypassed the plastic with copper wiring, then the speaker started working again. I think I may have uncovered a design flaw with the speakers. This picture shows the melted plastic: