Quite an impressive setup for such inexpensive earphones...how does it work on other iems? As to your low output impedance: I do understand that the ZS5 generally has very low impedance profile, which benefits from the low output impedance. As said, I shall try the ZS5 v1 with my dragonfly amp/dac (0.3 ohm output impedance), but my friend still has them. In theory, I should have a similar frequency response as you. But: out of the box, any iem should not require a complex setup. 95% percent of people run them on their phones (at least when not at home). And: I have some 50 earphones...impossible to tailor my setup to perfectly match each of them.