Clipping occurs when an amplifier stage cannot supply either enough output voltage swing or current to the load. It is not really related to frequency, except that speakers often have a lower impedance in a certain frequency range (usually lower freq) and that is where the amp would tend to run out of gas when attempting to respond to a high amplitude (loud) passage in that range. This has been discussed in other threads at some length, you should search. The result of the rapid change in voltage / current when the limit is reached, is generally a high frequncy transient (spike) that typically would just be too much for the high frequency drivers, thus fried tweeters. Such damage is therefore usually the result of inadequate electronics rather than inadequate speakers. It has also been pointed out in another thread that clipping can occur in any preamp / amp stage and have sonic implications, but is usually thought about with respect to the final amp because of the physical consequeces. :)
