Most speakers will sound fine right out of the box, but they will have a break-in period. I have even found some electronics have break-in periods. For example, the amplifiers in my car went through a break-in period, although it was not very noticable. The only reason I did notice it was because the day they were installed I was listening to a specific CD and I did not listen to that CD in my car again for about 2 months.
I have the 522-VAC; it took around 50 or so hours to break-in.