Just bought my son a 2003 Silverado Extended Cab LS in beautiful condition. The only issue with the truck was the front speakers, which were "crackling," so I assumed they were bad. I just got done replacing both woofers, and to my surprise, the "crackling" sound remained. Out of curiosity, I played a CD, which sounded perfect. For some odd reason, on AM/FM radio, there's a "crackling" sound coming from the speakers. It's not a lack of signal or static, as the radio will seek to the local stations just fine.

Any idea why the radio would "crackle" like this, yet sound perfect using the CD player? I assume that means it can't be the amplifier, or it would sound the same on all sources.