It just doesn't work that way, I wish it were that simple. The CSDs show large variances of decay for each given frequency which make up its decay profile, doesn't matter how fast an impulse response (at what frequency?) you can find. There's just no way you can get EQ to make one headphone sound exactly like the other, or even exactly what you want. At least there isn't any way for me, I have tried EQ multiple times in the past. Even when I forgot that I had EQ applied, after awhile I would feel the sound to be unnatural and wrong so I never use EQ anymore.