[BrendaAnnD]

Are you playing the radio out of the cabinet for these tests? If so, remember that if there is a significant low frequency component to the audio, the speaker will rattle or bottom out on bass notes with no baffle. This will affect the amount of at least perceived distortion. Try cupping your hands around the edges of the speaker and see if some of the distortion goes away. Alternatively, you could cut a speaker sized hole in a piece of cardboard and set this in front of the speaker.