EVENT TR6-N Tuned Reference 6 Monitor problem

Hey, I have a piar of EVENT TR6-N Tuned Reference 6 Monitor speakers and i think im noticing a little problem. When i play the "A" key on my keyboard, one of the speakers distort the sound. Makes it sound hissy, and fussy.....i dont know how to explain it, it just doesn't sound right. So to see if it was the speaker i turn the bad one off and the other one on and it sounded fine, switched the L and R outputs on the keyboard and it was still the same speaker distorting. The wierd thing is, is that it only sounds like its distorting only that 1 key....and not on all the sounds on the keyboard... any ideas? Thank you

Call event... [removed] x3 They are really helpfull, I've owned or own tr5, tr8, asp8 Good luck