Pros: SQ, 3D imaging, cohesive soundstage, isolation
Cons: fit could be bad for people with small ears
Driver - 3 drivers (3 way crossover)
Frequency response: 20 Hz -18 kHz
Impedance: 34 ohms
Sensitivity: 122 dB/mW
wipes, tool, soft bag, proprietary 2 pairs or silicon tips, 2 pairs of comply tips
Build Quality / Fit
The build quality I'm guessing is much better than the first version of the SM3 because I've read they had quite a few problems with them braking but I don't see much trouble with the newer version the SM3 V2. The housing which was one of the problem areas before feels like its make of good plastics and all the seems fit perfectly. Now there's a removable cable and its just like the ones UE and Westone use so finding replacements are easy if you have to do so. The cable its self is pretty much just like the one on the Heir 3.Ai with the same Y split, jack and braided cable so it feels well made also.
Fit I could see being a problem for a small few. The housing its self and the way the cable fits I could see people with small ears having a problem with getting them to fit comfortably. I think you'd be able to get a good seal but were the housing rests in the inside of your ear there might not be enough space but I think most like myself would be fine. Since they do fit me I have no problems with comfort and most shouldn't either.
Bass - In a word perfect, for me this is the type of bass I like. Its got plenty of punch and depth but in a controlled way and by that I mean it never feels to light or to heavy. There's enough punch for EDM and hip hop but its smooth enough for classical. I like to go up just a touch in the EQ or with an amp to give it that extra little something and for me that's the perfect fit and I haven't heard many IEM's with this kind of control. Now the Sony player I use with them has some of the best bass of any pmp I've heard but even on other players the SM3 still has the same control and feel.
Mids - The SM3 is know to have a more mid-centric sound but its not as forward as some that I've heard. They don't try and push the mids in your face, they do it in a more subtle way which makes everything sound in proportion. They isolate vocals about as well as the BA200 which is fantastic at that and midranged melodies and instruments sound perfect imo. Most of my favorite IEM's all have that warmer signature and the SM3 is no different and imo it makes music sound more realistic than the bright analytical IEM's. Detail is as good as anything I've heard and really I think the mids are also perfect.
Highs - This is how I like my highs, just enough sparkle that they sound crisp but never get to harsh but I have had a small bit of sibilance but that was do to the recording and not so much the IEM. With EDM you get all the high frequency detail but it never over shadows the mids which is the way I think good IEM's should sound because who wants to be blasted by bright highs that take away from where 70% or even 80% or the music is. Like with the bass and mids I also think the highs are perfect (you see where I'm going here).
Soundstage - Here's where the SM3 gets so much fun. The soundstage is above average but not technically the largest I've heard, I feel the RE262 was a bit bigger though it doesn't always feel that way. The SM3 surrounds you in the music with sounds coming from every direction and thats because it has the best 3D presentation of any IEM I've heard and I would be surprised if there's one better. With such a good 3D presentation it can make the soundstage sound bigger than its is and at times is sounds as large as the IE8 though I know its not, its sounds strange but when you hear it you'll know what I mean. The soundstage has become something I really focus on in an IEM and the SM3's is my favorite one by quite a bit.
Conclusion - Over all this is a great IEM with better build quality than the first version and with the removable cable you don't have to worry about the strain relief braking. Now as for SQ the SM3 is the best IEM I've heard and even though its priced anywhere from $300 to $400 I think its worth every penny. Its a great mid forward signature IEM with awesome detail and an amazing soundstage and the closest to perfect I've come across.