StaticV3 is correct though you bring up a good point, which is that the way rtings measure and present the data mean you can't see how much frequency response impacts the soundstage. It seems from your example that frequency response does make a big impact. I would find it helpful if rtings presented their soundstage score before and after equalisation to a consistent target (it wouldn't even matter particularly which one as long as it was the same).Curious how far they've placed Drop 8XX below HD800s, I thought they were the same thing. At least that's how they're advertised.
@Dazerdoreal I'm not sure, from my experiments modding Fostex RP headphones I've found filling in the 1-2khz dip is extremely difficult. I have found ways to lift the upper mid range and lower treble but 1-2kHz is quite stubborn. So I have wondered if, for the planar magnetic headphones at least, there is some aspect of their design which makes this difficult rather than being on purpose.