Check out Ian Dunmore's (@Torq) review of the Sennheiser HD 820 as part of The HEADPHONE Community Preview Program in the link below.
The Sennheiser HD 800 and the HD800S are legendary headphones in the headphone community. The brand new HD 820 Closed-Back headphones from Sennheiser looks to join them and by all accounts, is going to fit right in at the top! Featuring the sound you know and love in the HD 800 / 800S in a closed-back package, its pretty hard to go wrong the HD820.
The Sennheiser HD 820 has incorporated concave glass covers over its drivers to deliver up to 26db in passive noise cancellation. Not only does the concave glass help reduce outside noise, it also acts as a resonance reducer by reflecting sound to a dedicated absorber. You can also see through the glass and see the inner-workings of the HD 820 which is an absolutely gorgeous pair of cans. Because of the concave glass, the closed-back design of the HD 820 makes it one of the most versatile high-end headphones on the market. Whether you are using them for musical enjoyment, mixing and mastering or on the go, the HD 820 are flexible to your needs.
The HD 820 is lightweight and has premium microfibre earpads, much like the HD 800 and HD 800S. It has the trademark metal headband that the rest of the HD 800 series has along with an internal damper that offers improved comfort and stability while wearing the HD 820. The Sennheiser HD 820 ships with 3 different connectors. The standard 1/4" connector and 4-pin XLR but the third connector is special as is something we should start seeing more of with Flagships in the future. The third connector is a 4.4mm Pentaconn termination. This plug has 5 contacts for a balanced connection and the 5th contact eliminates grounding issues. This is a plug that Sony has been pushing for a while in their DAPs (Digital Audio Players) and we're glad to see companies like Sennheiser starting to adapt them.
Sound-wise, the HD 820 are up there with the best. They manage to maintain most of the incredible soundstage that the HD 800 and HD 800S are famous for while being impressively transparent with a tight low-end. The low-end on the HD 820 is stronger than on the HD 800 however, the HD 820 are no by no means bass cannons. For a closed-back headphone, you could even describe them as bass-shy. But their shear detail and clarity are unmatched in the closed headphone world and if you are looking for your closed-back endgame, look no further than the Sennheiser HD 820.