I think part of it is conditioning. The HD800 is probably the most open sounding headphone out there. That means in part, there is not a trace of boxy or resonant there. Even open cans like their HD650, which are likely less open in construction, could appear "boxy" for a number of reasons after listening to the HD800. They have more pronounced mids, less extreme highs. To have that alone can cause some perceived boxiness. The simple fact that more air gets out of the HD800 vs. anything is another factor. You're literally "spoiled" by it. Someone who has not ever heard the HD800, and perhaps only heard other closed cans, regardless of price, MDR-Z7, Z1R, Fostex, Audio Technica, Closed Audeze, you name it - let them try the HD820, and I'd bet you'd never hear them say boxing or nasally. I recall only the Sony Z1R, the Eikon and maybe one other sounding as low in boxy sound as the HD820. Take that into consideration here.