Amazon.com: beyerdynamic DT 770 PRO 80 Ohm Over-Ear Studio Headphones (Black) with Knox Gear Compact 4-Channel Stereo Amplifier Bundle (2 Items) : Electronics
Headphone Impedance Demystified: Do I Need a Headphone Amp? - Headphonesty
Archimago's Musings: MEASUREMENTS / MUSINGS: Headphone impedance, sensitivity, efficiency, and amplifier output impedance. (And a quick thought on Darko's "All You Need Is...")
How to explain Ohm like I'm 8. The HD800s is 300 Ohm. The Spirit Torino Super is 32 Ohm. Same pricing at $1600. What does it mean with different Ohms? : r/headphones
Amazon.com: beyerdynamic DT 770 PRO Headphones (250 Ohm) Bundle with Compact 4-Channel Stereo Headphone Amplifier (2 Items) : Electronics
Headphone Impedance Demystified: Do I Need a Headphone Amp? - Headphonesty