The Sennheiser HD-820 is a closed-back version of the legendary HD800 headphones, and uses some innovative technology that makes them stunningly transparent. Closed-back designs have historically suffered from unwanted resonances, while open-back designs, famed for their natural, transparent sound, can leak audio and let in ambient sounds...

In 1991 Sennheiser released the Orpheus, claiming they were the world's best headphones. Most serious critics agreed. Originally costing $20,000, only 300 were made, and a set in good condition today will fetch around $50,000. Now, 25 years later, they are doing it again. A team of their best engineers were given 10 years and a virtually ...