The dealer initially sent a tech man down to investigate with instruction from Focal. He found that on each speaker there were two stripped screws that hold the side panel to the main cabinet. When certain vocals are played such as Gail Pettis...it is quite audible! Second pair has a much better midrange, hence aren't vibrating as much...but still do! Time line is about a couple of months to wait this out for an answer. Something in assembly has gone wrong...they don't do it with all vocals...Krall, Holly Cole, Nora, etc. seem not to resonate...but a few others certainly do!! I would think this to be rare in a speaker that has been out for so long!