Sennheiser CX Sport Review: Can’t Shake ’Em

Testing workout earbuds requires an entirely different set of metrics than regular in-ear headphones. More than anything else, workout earbuds need to stay put. Running is hard enough without constantly flibberting with something in your ear canal. Other factors that might be big pluses when you're sitting at your desk are not so great when you're in motion. Excellent noise filtering is less attractive when you might get mowed down by a cyclist.