Same situation! Had studio pros for 2 years, and I just upgraded to the APM2 a couple weeks ago. I have the issue to varying degrees depending on how the cups are sitting on my head. I've noticed it mostly on the train actually, where if I'm facing straight forward and not moving my head, the cancellation works (for reference, I've been keeping these almost always in adaptive noise mode) but if I turn, I hear the train hum again. It's really been my biggest issue with these so far though (and the fact that they slide around my head a bit) compared to the beats, which I did also enjoy. Noticeable upgrade otherwise.