Sennheiser's HD650s: Classic headphones bundled with Groove DAC...why? - The Audiophile Man
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 | Sennheiser
Sennheiser HD650 Review – Too Expensive in 2023? - Home Studio Basics
Sennheiser HD 650 Review: Beautiful and Premium Studio Headphones
Sennheiser HD 650 review - SoundGuys
SENNHEISER HD600 vs HD650 A compartive review – also featuring the AKG Q701 | The Headphoneer
Sennheiser HD650 Reference Class Stereo Headphones