break-in of speakers is definately noticeable - I think you need to give them a month of serious volume before they settle down.
depending on the speaker, there is always one frequency range that dominates - my Creamback G12H-30s (55Hz bass cone) sounded REALLY thick and bassy when I first got them reconed, but the top end really opened up after a while. The G12H-30 (anniversary series) with 75Hz lead cones sounded really midrange-heavy at first, then settled down too, but probably had just a little bit too much top end for me (hence I use 55Hz bass cone versions now)