I am having exactly the same issue with one of my Airmotiv 5 speakers. It started randomly, and then went away for several months, but has since returned. I was going to try and take apart the speaker and see if there is anything noticeably loose, but if someone else is having the same issue, it could be beyond something I could easily fix myself. Emotiva said they would take a look, but given that they are outside of warranty, the cost wasa minimum $100 (if I remember correctly), plus the cost to ship the speaker from Canada. Add in the fact that it may not produce an issue when checked, I could pay $150+ and end up with the problem returning soon after.