Tested mine also and there is definitely a rattle in the left ear cup upto around 30Hz then it dissapears. Such a shame as they are more analytical, well rounded mids,sparkly and have slightly more soundstage compared to my ATHAD900x. How do we start RMA or request a refund? Or Should I wait for these drivers to break in before jumping the gun?
Have exactly the same rattle as you in my left ear cup from the 0Hz-70Hz test. Though I'm hoping to give them a chance to break in and hopefully the rattle will go away.
Also waiting an official response after MD get in touch with AKG after Xmas about procedures.