First impression is that the UM3x seems to isolate noise (lots at Stereo
I actually quite like the sound from the UM3x, it is warm and easy on the ears. Soundstage is decent compared to my Audio Technica CK100 ( Yes, CK100 has a wider soundstage) but is full and tight compared to the W3 which to me is a little bloated and muddy. The vocals felt slightly more forward compared to the W3 although I think that is mainly because the UM3x is overall clearer and cleaner in presentation compared to the W3.
Specification wise, although the UM3x is higher in impedance but it is also higher in it's sensitivity so I didn't feel that the UM3x was much difficult to drive, still the UM3x produced lesser hiss (5%, maybe 10%?) on the iqube on low gain setting.
I will drop over this Saturday to test again as I might consider getting this for my wife. ( I can use this when she is not....











