squeak from rear speakers

[Nyck]

When i am listening to rap or something with a good amount of bass i hear a temporary squeaking noise when it kicks in....is this bad wiring or bad speakers? here is the best pic i could find of my kenwood speakers.

http://img.photobucket.com/albums/v257/NyckXD/Nyx/KEY70002.jpg

[sed]

check the torque of the screws holding the speaker in, might be a little loose and at first bass hit they wobble a tad, then settle in....

or a tweeter is blown.

shawn :)