I just received my ZS3 today (22 days Switzerland Post to Canada), and although one side didn't sound hollow, something was not right. Off I went to Audiocheck to do some investigating, and sure enough, the polarity test showed the left one had the cable plugged in wrong. Who the heck...oh I did that! I fixed it and have been enjoying these top notch IEMs ever since. Head over there and test yours. I'll review these when I take a breath from this sweet music.