Sennheiser HD 650 Open Back Professional Headphone 508825, NOB New Opened Box Condition. Description The audiophile HD 650 is the ultimate in open dynamic headphone design. Developed from the award-winning HD 600, the HD 650s improved materials for even better sound reproduction They captivate the listener with their expressiveness and emotion while maintaining absolute precision and lifelike reproduction. Enjoy sound in all its perfection. Features Balanced & transparent sound Elegant titanium-silver finish Optimized for hi-resolution re