What is actually going on to make some headphones have a larger soundstage than others? I'll admit I have no idea.
Does the recession of mids have anything to do with it? For example, the DT880 has slightly recessed mids relative to the bass and highs. It does sound like there is a sense of space because of the 'hole' in the midrange, whereas something like a HD650 fills in that hole and thus sounds more congested...? I'm not sure if the K701 also has a similar 'hole' in the midrange, thus enabling it to sound bigger?
Does it have to do with 'instrument separation'? If so, how is instrument separation actually achieved? Is it by increasing the treble, and thus gaining increased transient response and detail?
Is it, in fact, as simple as the physical space between your ears and the drivers? The K701, for example, has very thick pads so the drivers are far from your ears, and Grado's have very thin pads so the drivers are right against your ears. No surprise that the K701 has a much larger soundstage than most Grado's, but is it as simple as that? For example, if you could somehow use Grado pads with the K701, and K701 pads with Grado's, would the K701 now have a smaller soundstage than the Grado?
Thanks in advance for helping me to understand this!!