This has been a fascinating experiment. I understand why people own multiple sets of headphones now. I picked up the Sundaras and HD-6XX to compare. The Sennheizers are down to $220 on Drop. They really couldn't bed much more different. In the end, as much as I'd love to save $80 right now, the HDs are going back. I can certainly see how people might prefer the HDs; they're much more lively. It's not like live music, but you can still feel them a little bit. Particularly on the low end, as there's still some air moving. You don't really feel anything from the Sundaras.
When I first listened to the Sundaras my first thought was "where's the bass." Turns out it's all there. You just don't feel it. They can actually reach down halfway deep, but it's a completely different thing than what you're used to. That having been said, once you get used to it they're wonderful. There's a fidelity across the entire spectrum that I haven't heard from typical speakers. You never hear frequencies step on each other, so you get great clarity even in busy music.
Listening to Eva Cassidy's rendition of Wayfaring Stranger you hear great tone on the bass, subtleties from the guitar, and still clarity from the high-hat and cymbals.
Listening to SATO/DoaM you can hear different aspects of Rhodes's guitar tone, including a bit of overdrive. Never noticed that before. And of course Bob Daisley's fine basswork
Take Your Whisky Home has a lot of vocalizations I'd never noticed before. Not surprising, but you're not used to Dave being subtle.
Interestingly, it was Deftones that really sold me on the Sunduras. The bottom end on White Pony is massive, but you still hear nuances all over the place. Also, I think I heard Chi Cheng playing a fretless bass. Never picked up on that before.
I'd love to find some cans that combine both qualities, providing that precision while still being a little palpable, but I suspect that's where the price goes through the roof. But, that's honestly what big-ass speakers are for. Not really an option for me right now, it'll be a few more months, but turning large speakers up to 11 is still the way I prefer my music. There's definitely something to be said for just listening like this, though. It's like having music injected directly into your brain, rather than being bombarded with it. The more I get used to it the more I appreciate it. At some point I'll get my big stereo back, but it'll still be nice to have these. A big reason for sticking with the Sundaras is that once headphones become complimentary, rather than primary, I'll want as much clarity as I can get from them.