I recently picked up 2 R800F speakers, and the tweeters, I notice, only at specific frequency makes a slight scratchy sound. It does it at any volume, with multiple different melodies. Some may not notice, but I certainly do. Not sure if it's the receiver(Denon avr x4700h), or something else. I would like to find parts, and and if anyone has experience pulling the horns, is there a diagram or something available? Be gentle, I'm new to this speaker line.