It seems odd to read this as your head would get bruises or worse.
Also, all speakers today work by moving a diaphragm, cone or surface to create sound. A drop would impart mechanical energy and thus distort sound. This means almost everyone I know would not call distortion due to a drop to be a design flaw.
So, I have bought these headphones a year and a half ago. They are great, except for one thing: they are very, very sensible to drops. If I accidentally drop them from 30-40 cm above ground, they will get some kind of sound distortion, let's call it. It happens at higher volumes, but that doesn't really represent a very big issue to me, as the sound it already very loud, even at 25% in Windows. What is a very big issue, though, is the fact that they (sometimes, can't really predict when it will happen) suddenly lose a lot of the bass and the audio sounds very 'washed out' and unclear. I have another pair of the exact same headphones and those don't have the issue and I would like some help to fix this issue.
Also, I'm pretty sure I didn't post this issue in the right subforum, so feel free to move it around.