Steve,
I'm surprised that they are active. I've owned both the 540 and 550, and I along with numerous other keyboardists (friends of mine) who played both models all felt that they were for show.. I've even covered up the main part of the speaker and placed my ear flat against the tweeter and heard no sound from either model.. It just sounds like I covered up the main and only functioning speakers.... If they are working, to date I have not heard anything from them.. I even tested them in stores.. Even had store salemen saying they too thought there were just for show because they couldn't hear any sound from them..

Squeak