I got these pioneer speakers that came with the car when I bought it. They are 6.5" coaxial 3 way speakers. Recently they have been distorting(only one of them actually) and I'm not sure if its the panels resonating or the speaker needs to be replaced. I can hear the distortion on bass notes only but if I apply little pressure on the rubber surround or cone woofer part of the speaker it goes away. BTW, I'm running an Alpine 9856 head unit only.

 

Make sure the speaker terminals arent grounding out on the metal of the door or the speaker tips arent contacting the basket of the speaker. If theyre installed correctly, then you probably should go get some new speakers.