There are some microphonics if you tug on the cable, but they are worn over the ear so its nonexistent most of the time. I really doubt there are many people here who have both at the same time because they carry the same sound signature but are presented in a vastly different way.
The closest would be ceph who has owned the sm3 first before owning the um3x.
there is no VS between this two for me, the sound of the sm3,when i heard it again from aizen's pair still has that enveloping effect on me, i guess part of me still wants that relaxing sound of the sm3. never tried sm3s on rock music so i cant shed light on the rock + sm3 combo.
the um3x for me has greater instrument separation, still that non-fatiguing sound sig and makes it a different beast from the sm3. not saying the sm3s are fatiguing to my ears, maybe it is because of the shell and the sound that doesnt make you wanting more...
sm3 or um3x, both are winners, i just cant keep to iems at once... im not kalikot you know...
