[atoav]

To get the same (perceived) amplitude a low freuquency wave needs much more power than a higher frequency one. In a speaker most power is used in the low end while the tweeters use just a fraction of it.

This means that given any kind of regular music played on this speaker the created air pressure differences will be much higher for the bass frequencies than for the treble frequencies.

On top of that the difference in wave length also changes how it interacts with materials. The long bass wave bends around corners and goes through walls (which is why you can hear them two rooms over), while the shorter treble wave is bascially reflected by even a thin wall and looses energy fast in free air.