the cross over networks just filter the frequencies to the right speakers, but they are not mandatory, the tweeters will probably have a capacitor across them which effectively does the same thing that you would get in the cross over. i know the k11 factory speakers have these capacitors. if the capacitor has come loose, or taken the wire with it then it could be causing the problem. best thing to do is get the tweeters out and see if there is anything obviously wrong with them