Sports headphones have to be strong in quite a few disciplines. They must be impervious to rain and sweat. They should tolerate being treated with sporty roughness. And they have to stay securely and comfortably in place, even during the most intense workout moves. Should they, on top of all that, sound so fantastic as to propel you to new personal bests, you can be quite sure that they are the product of Sennheiser.