1.a hi-fi enthusiast.
So by this definition, if you enjoy the K550, they are up to audiophile standards. Considering the K550 pretty much sounds like a closed K701 with more body in the low end, I don't see why anyone should get bent out of shape for calling them audiophile quality. After all, once upon a time the K701 was a high end audiophile quality flagship headphone. Semantics can be a b**ch. That's why in all my years in this hobby I've never considered myself to be an "audiophile" because people wonder why I use $800 headphones to listen to Spotify and not massive HD files that eat up hard drive space. It's what you enjoy, that's all that matters here.