The HD 600 is STILL one of the best headphones.

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Sennheiser HD 600 - Reviews Headphone Reviews and Discussion

Sennheiser HD600 Wired Audiophile Headphones Reviewed - Future Audiophile Magazine

A Sennheiser HD 600 time machine story, Sennheiser

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Sennheiser HD 600 - Reviews Headphone Reviews and Discussion

Sennheiser HD600 Open-Back Headphone

An underrated cheaper alternative to the HD600/HD6XX - Audio Techno a R-70X : r/headphones

SoundStage! Equipment Review - Sennheiser HD 600 Headphones (1/2003)

Sennheiser HD650 vs HD600 Review & Verdict –

Sennheiser HD600 Review (Headphone), Page 17