Audio Systems: car speakers, alpine cda 9835, dull thud

Question
have alpine cda-9835 car stereo and 2005 mb quart 5.25" separate front speakers with tweeters. the speakers seem to make sounds almost like they are hitting the plastic covers over the speakers when the bass hits.  I can't turn it up as loud as i would like when im jammin.  Ive adjusted everything including the equalizer but I think it has something to do with the active crossover control in the tuner. do u know the suggested settings of crossover for the speakers? or is it just hitting the cover and need to buy special coverings?

Answer
Danny,

   it actually sounds like a voice coil problem which can range from a dull thud to a pecking sound... adjust your crossover for a good mid range sound instead of the usual low tones in the 30-80hz range... if the adjustment doesnt work i would try a new set of speakers , if they are fairly new they should be covered under a warranty so you can get a replacement set with no problems ... hope this helps you out

thanks