2001 Eclipse GS Speaker problem

Hi all,

this might not be the correct place to post such an idiotic question, but i am having slight trouble with my factory installed infinity stereo and speakers on 2001 eclipse GS. The sound from speakers has gone to the dumps lately, it distorts a lot. When i direct all output (fading) to rear speakers, it goes away, however, the sound is barely audible then. On this car, i seem to have 2 speakers by the front mirrors, 2 front speakers on each door, two speakers in the rear, and one center speaker. I suspect that problem is coming from the center one (not sure what its function is, if someone can educate me it'd be helpful). Is there a way i can fix this problem w/o installation new speakers?

thanks for the patience