Having the problem in both doors as well. The bass note has to be just right (and not necessarily very loud). I think (at least in my case) that it's the aluminum trim in each door. When I brought my car in last week, I said I was getting this "hooptie" effect and asked them about reseating those two trim pieces. Without saying as much, I had the same reservations as TX about digging into the doors. They apparently agreed because they decided not to try, explaining that they thought they might make the problem worse until they better understand the trim. They said they'd first try to take the trim off of their own demo to explore the possibility, but I haven't yet heard back on that. I didn't deem it that pressing an issue to stay on top of them about it. I don't think it happened at all over the weekend (or I'm starting to block it out!).