It's worth repeating that the only headphone Fostex aimed at the audiophile market was the 1978 NA-market T50. All the rest are meant strictly as pro audio tools. You're not supposed to be using them, you're not supposed to know about them, and you're not supposed to expect them to sound as good as it turns out they can sound. Any goodness we get from them is over the fence and under the table.
Does that help at all?
I'm fine with modding, so I may take the suggestions aimed towards that. But I'm still pretty confused about which changes yield which results. My YH-3 mod was kinda like "shoot in the dark. Turn on the lights, see what I hit. Turn off the lights, shoot again. Turn on the lights, see what I hit."