Sennheiser CX SPORT Wireless Bluetooth in-ear in-ear headphones. Experience the joy of moving with Sennheiser's new CX SPORT wireless in-ear headphones. With an ultra-light design that is resistant to splashes of water and sweat, these headphones can be worn on the nape or front of the neck. They feature advanced Bluetooth technology that allows you to experience high-quality sound while on the go.