Frequencies over the sub's rated freq response will not be reproduced accurately in sound, they are converted to more & more heat and could contribute to coil failure. You can still hear some of the mids, but a majority of the power is converted to heat. If you are playing at low volumes it wouldnt hurt too much, but once you start really pounding all that excess heat can really make a difference.

It will also seriously color your bass notes and sound really crappy...