I had already the old model (CX680) that I used to do my jogging, a great product for those who play sports, because even after several tens of kilometers, the headphones remain in place despite perspiration.
Super convenient because you can go under water without fear of damaging it.
I have only one criticism but perspective, if I compare to the old model, 'bonnets' provided with, on the old model I found two sizes that fit me very well, so I a small lodge my worries was not quite the same size / shape on each side of my head, and this model not find my happiness. Well after going to know if it comes from my ears or studding.
Then next sound reproduction:
I love good sound reproduction, I drive with Alpine / Focal, its processor, etc ... so I am rather difficult. This helmet is a small marvel, his centered, very good record low as well, as the mid / high section. You clearly hear the same voices on pieces techno / dance which have low preponderant.
To summarize, you love her, you run (20 kilometers I regularly cold weather as very hot)? If yes then this headset is for me to have the product, it is closer to 5 stars than 4 stars but have to leave a little 'game' Sennheiser was able to place the final product :) Probably the best price / quality for musical runners'.
David