Probably not the cause of the rattle. I haven't heard a rattle in this pair but I sent a pair to akg to be repaired for a rattle. I know the rattle was in the driver itself. It took a lot of volume and bass to hear the rattle.
I have k702 and I took the ear pads off today and there is a white ring that goes around the driver. What is that for? Is it to give more bass or does air pass through it? It had me concerned because it looked like there is a crease in the middle of one of the sections.