HD650 Open-Back Audiophile Headphones, by Sennheiser | Audio Sanctuary
Sennheiser HD 650 review - SoundGuys
Amazon.com: Sennheiser Consumer Audio HD 650 - Audiophile Hi-Res Open Back Dynamic Headphone, Titan : Everything Else
Archimago's Musings: MEASUREMENTS: Sennheiser HD650 (~2010-2012) and HD800 (~2010). A comparison of two "Reference Class" headphones, and a look/listen to the "Sennheiser veil / darkness". [Inexpensive 2TB SSD and inflation in consumer electronics...]
HD 650 : PA / Studio Headphones Sennheiser Hifi - SonoVente.com - en
Sennheiser HD 650 review
Sennheiser Replacement Complete Headband for HD650