I havent had my car that long but can already tell the front speakers/tweeters are trying t send bass through them and show signs of maxing out/distortion when turned up loud. Thought that was kinda weird being it is a "tuned system". They may have needed the sound curve to balance the system but it seems there would have been a better way to go about it.
Scubatch- Is that why you replaced yours?
The answer is clear - if you look at the natural frequency response and rolloff of the stock audio system, the dash speaker is anything but a traditional tweeter. There have been numerous threads here about what changing the speakers in a Sonata can do, including trying to put tweeters in the dash.