Why do speakers make crackling noises when the pitches get too high for them? And why is it that lower end speakers tend to crackle more? If you try to feed in too high of a frequency, I would imagine the magnet just physically wouldn't be able to oscillate fast enough, but I don't know why it would make such a hideous noise.
As you increase the frequency of the electrical audio signal being fed into the loudspeaker beyond its intended range, mechanical feedback in the oscillation of the electromagnet driver itself can result in out of control vibrations of the electromagnetic into its magnet frame so that it's literally rattling around to some extent.
Quality speakers divide the frequency range over multiple specialized drivers housed in a single enclosure and uses a filter network to partition the input signal accordingly and deliver each part to the right driver.