Amazon.com: beyerdynamic DT 990 PRO 250 ohm Studio Headphones (Ninja Black, Limited Edition) with 4-Channel Headphone Amplifier Bundle (2 Items) : Electronics
Amazon.com: beyerdynamic DT 770 PRO 250 Ohm Grey Over-Ear Studio Headphones. Enclosed Design, Wired for Professional Recording and Monitoring with Extra Grey Velour Earpads (Bundle) : Musical Instruments
Black DT 770 Pro Limited Ed. 250 OHM Headphones | Unclaimed Baggage
Amazon.com: beyerdynamic DT-990 Pro Acoustically Open Headphones (250 Ohms) and Knox Gear Compact 4-Channel Stereo Headphone Amplifier Bundle (2 Items) : Electronics
Beyerdynamic DT 770 250 Ohm Studio Headphone Review - Sonarworks Blog