I own this MacBook Pro, which was bought in Germany, and I am currently residing in China, where I accidentally switched headphones with a Chinese friend. Both are official Apple EarPods, mine came with my iPhone 5, which I also bought in Germany, and hers came with her iPhone 6, bought in China.
At first I did not notice our headphones had been switched, because they look the same. However, when plugged into my MacBook, the sound was just not right, as if the trebles had been removed from the music, resulting in songs without singers. When I tried with my iPhone and my other friend’s MacBook Air (bought in China), there was no problem whatsoever. I was worried that the headphone jack hardware itself had been damaged, but other headphones worked, so I concluded that both headphone jack as well as EarPods themselves were usable, just not together.
Later I asked the Chinese friend if I could see her EarPods and tested them with my MacBook—again, no problem whatsoever. I then inspected the headphones closely: They sure do look the same, but the insulating plastic rings between the conducting rings at the plug itself are white on my German EarBuds but black on the Chinese ones. This is the only difference I could spot, even though I felt like the Chinese ones just did not fit 100% into the socket, thus resulting in some wrongly connected conductors leading to the strange sound.
So why do the Chinese EarPods not work with my German MacBook even though it is supposed to be the same standard?