Transcription from the Head-Fi TV video about the MrSpeakers Alpha Dog (emphasis added):
Now the most amazing thing about the Alpha Dog to me is not just how it presents all that detail, it's how it does it and sounds like an open headphone, even though it's a closed headphone. If you were to put this on my head in a silent room, with my eyes closed, I'd never heard it before, you put it on my head, I would have guessed I was listening to an open, circumaural (or around-the-ear) headphone; because that's how the soundstage sounds on this. It's not quite as biiiig and airy as an HD 800, but, really, not much is; but I would guess "open headphone." It sounds like an open headphone and it's closed.
I absolutely stand by that. I've been listening to this headphone (either the prototype or the production version, as I bought both) almost every day since they arrived. The reason I qualified that statement with "in a silent room" is because it's the only way to keep out the obvious external cues that quickly give away either an open headphone or a closed headphone.
If you're listening with an open headphone, and there's noise around you, the open nature of a headphone is given away immediately by the clearer intrusion of the ambient noise. Same with the muffled versions of those external noises when you're wearing a closed headphone--those smothered sounds making the presence of the closed cups obvious.
The more silent the room, the fewer the external cues play into it. And in my quiet office downstairs, I simply forget I'm listening to closed headphones with the Alpha Dog. I'm there now, at the moment listening to Beirut's "East Harlem" (from the album The Rip Tide), and the Alpha Dog images openly enough--and the closed-cup acoustic invisible enough--that this headphone does image more to me like an open headphone than a closed one, for sure.
If you hear it differently, that's fine. But I called it like I heard it, and still hear it.