You're likely simply hearing more resolution from your system, only uncovering something that was already there. You need to look at your system as to cause.
Sibilance in recordings: your experience the same?
I have just finished a remodeling project and added new 20amp lines to feed my system. Rather suddenly I became annoyed with excessive sibilance on Patricia Barber's Mythologies recording (CD). I had never noticed this before. I looked at my system configuration and could find no obvious changes in the pre/post-remodeling arrangement of my power cords and ICs, so I have to ask if others have had the same experience with this recording. While I'm at it, are there other recordings, say, in the female singer/songwriter genre with inherently excessive sibilance? The really annoying thing about sibilance is once you hear it, YOU REALLY HEAR IT!