Also, if its range goes well outside of the limits of hearing, then that would suggest that it's not struggling to reproduce the frequencies that are at the very ends, in other words they're suggesting that its response curve isn't rapidly dropping at 18 kHz if the driver can actually reproduce 30 kHz. A frequency graph would be more useful than just saying 5-30,000 Hz. There's never any context of +/- x dB attached to those "specifications" either. I would pay little attention to those unless it's quoting figures that are within the 20-20,000 range. If its quoted range stops within those frequencies, then it will probably have a deficiency at that extreme that would be obvious to anybody.