You would not want to feed low bass (including subsonic bass) into a speaker designed for 1k-5k hz. Feeding it anything above 5k would not be as much of a problem, but you definitely do not want to send low bass as that will cause the driver to distort as it attempts to play frequencies below the bottom of it's range. This can ruin the driver very quickly. I strongly suggest that you either use a crossover before the amp (or at the amp) or at the very least, put a high-pass filter on the midrange to keep low frequencies out of the midrange which will allow it to operate at it's designed wattage safely. You can buy cheap in-line filters for a few dollars.
edit: thx Brian, you beat me to it
