Sennheiser HD 660 S Open-back wired over-ear headphones at Crutchfield
Sennheiser sells off its consumer brand | TechCrunch
Amazon.com: Sennheiser HD 800 S Over-the-Ear Audiophile Reference Headphones - Ring Radiator Drivers With Open-Back Earcups, Includes Balanced Cable, 2-Year Warranty (Black) : Electronics
Amazon.com: SENNHEISER HD 4.40 Around Ear Bluetooth Wireless Headphones - Black : Electronics