Couple of words and a star-map for 820
From the first sound, the character of the 800 S is recognized. Except that some booming characteristic of closed headphones is initially annoying, but very soon the brain switches - it stops to highlight this moment. So perhaps even at the level of the difference between the instances with 800 S, it is possible to estimate the volume of the difference, with some "correction to the wind" - a slightly smaller soundstage and a slightly more cheerful bass.
Personality. The treble is sharp-ish, slightly more embossed than the old version of the 800. The bass is clearly and unambiguously present, is sufficient in volume, without going over the border, fast and structured, from the best that I have ever met in dynamic cans. Mids perhaps a little smoother and exactly closer to the listener than in the 800 without S. The soundstage is quite standard, not bad in volume for closed cans, but without "stadium" vastness.
For comparability of the results, I listened to headphones with a 6.3 stockcable. But for real-world listening, I strongly recommend changing the stock cable immediately. In my case, the replacement was the RLS-7 Art-Cables XLR-4 version. Everything is getting better in the sound – greater clarity of mids, more balanced treble, more legible and faster bass (without loss of volume), a wider soundstage. Of the disadvantages – only the weight of the cable.
Metal
Black, Death, Grindcore. Is the consciousness completely poisoned by isodynamics so much that it does not allow dynamic headphones to reach to the highest heights on extreme metal? Even despite being painted black? Perhaps this is the case. From the objective side, we will add a slightly lower speed than that of the champions and the absence of a "feature" that allows you to climb up due to a certain coloration (adding raw rage, for example), we have a too monitor approach similar to the 800 S.
Thrash, Alternative. On thrash and alternative, the impression is different from the 800 S, which seemed too calm - 820, unlike them, they fall in enthusiastically and moderately fun.
Doom. 820 is played with a sufficient proper fat level for the Doom. No, I can't call the performance uber-outstanding and throwing isodynamics into the dust, but it is quite satisfactory for the top level cans.
Sludge, Stoner. On the sludge - everything is great without any reservations. Undoubtedly heavy metal, sludge is among the sweet points of 820.
Progressive, Symphonic. Prog and symphonic - simpler than 800 S. Naturalness, balance and calmness, thoughtful and measured. But it is less spacious than the 800 S can do.
Power. Lack of a dash of cheerful stupidity for an ideal.
Goth. Melancholy is a good place, but too flesh-saturated melancholy. Not quite meeting expectations, an imperfect hit.
Industrial. Cool-cool, fast and mobile, moderately voluminous and percussive bass. Delicious. To make it absolutely delicious for me, I would prefer a smoother sound signature, to slightly remove the meat in mids / mid-bass.
Electronica
On electronic music, perhaps both the 820 and 800S and the good old 800 are equally beautiful. 800 is a little nicer on ambient or something minimalistic and thoughtfully unhurried. The calmer and more sprawling nature of the 800 allows you to inhale Oxygene from Jean-Michel Jarre with a wide chest amplitude, with taste in every inhale and exhale, a tickle in the stomach. 820/800S is noticeably preferable on more vigorous genres, energy and drive are charged more efficiently, acceleration of electronic charges is enough to penetrate into the farthest corners of the listening body. Even in winter, Infected Mushroom will wake up the desire to grab a mushroom picker's combat machete and rush into the woods to collect a fragrant harvest of aspen, birch, and other white and black pears.
Jazz
Good, but no more. Although no less. Everything is in place - on the one hand, it is impossible to be sure of any obvious technical mistakes. But there is not enough "spark" to make it really good, to a really outstanding result on the genre.
In a word – very, very good closed headphones. I don't really understand the disappointment that I met in some reviews on them. I would boldly recommend it to fans of the generic sound signature of Sennheiser, who want to get them in a closed format.
