At least a couple of years ago, I bought an M8 for my Dad. For some time now (maybe since last summer), he's hearing a random transient thump coming from it. I've heard it myself over the holidays. It is short-lived (lasts less than half a second, probably less than 1/4 sec.), and only happens once in a while. Maybe between once a week to a few times per day. I can't tell if it is coming from the driver or an internal component. I am leaning towards the driver. Any ideas what the problem is? I'm quite confident it is not in the source material. It doesn't matter which source is selected.