Beyerdynamic - 'DT 770 PRO' Closed-Back Studio Reference Headphones (80 Ohm). Beyerdynamic - 'DT 770 PRO' Studio Reference Headphones, Closed-Back, 80 Ohm, 5Hz - 35kHz, 45mm Driver. In the early 80s, beyerdynamic achieved a real milestone in the history of audio technology.
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