I have been playing my sm64 for about a month. During the use once in a time i switched one to another with my sm3v2. For those who still wanna know the difference between the two...here is my impression from both iems:
(sorry my english is not that good, but i will try to describe as good as i can )
The source i am using:
Iipod classic wav+alac files, Alo National amp, Alo RxMK3+clas db, Fostex HPP1, Govibe Vestamp and Govibe Vulcan+
1st thing to notice, the gain of sm64 is higher than sm3v2. Short way to say, with sm64 you will need to use an amp to make it really sing. Otherwise you will not get the most out of it during listening. If you drive sm64 without amp (or direct from ipod), the mids and the bass will not come alive, the treble will be dominant and that will leads you to a brighter sound and loosing its body from the sound.
The highs on sm64 is more sparkling (but still smooth) compared to sm3v2. But it does not mean of being too harsh during my listening. For those who really like the highs on sm3v2..the highs on sm64 could be the hate. But to me...i find the highs on sm64 makes the sound is more lively. Is more musical and fun. For some jazz songs..yes i find sm3v2 could be the winner here, but not always. But still, sm64 is more fun sounding IMO. What i mean by "fun"..is an audiophile kind of fun..not a Beats's fun. For those who feels sm3v2 recessed in highs..so this is surely for you.
The mids on sm3v2 is more creamy. Is thicker. and more forward (just a tad) compared to sm64. I know..for sm3v2 lovers (including my self) will miss its creamy character when upgraded to sm64. What i love most about the song...is vocal. Every time i listen to the song...i always concentrate to how the vocal is presented and then i will give my judgement on whether or not i should keep it. Well...this sm64 is surely worth a keeper. The mids on sm64 is different from sm3v2 but not totally. It is a bit more sharp while sm3v2 is a bit more rounded. Don't get me wrong...what i mean by sharp is like the vocal is somehow more refined..is more well pronounced added with crisp and more transparent as well. I really don't know the right words to describe it..but i hope you guys get what i mean.
The quantity of the bass i think is about the same. But this time...sm64 is able to deliver a more tight bass and it can go deeper than my sm3v2. The bass is more cleaner and a bit more punch (not bloated) compared to sm3v2. I think the bass of my sm64 is better than my sm3v2.
Sound-stage + Instrument positioning:
Soundstage is the same and i think they both are good. But for Instrument positioning i will give the score to my sm64 due to its clarity and detailing is better than sm3v2. I find the sm64 has better resolution and layering on the music compared to my sm3v2. But not by much.
So if you guys asking me which one better for direct use to ipod (or any other players)..my would say SM3V2 will surely better for direct use. The sm3v2 is easier to drive than sm64. My self..i often use my sm3v2 direct to my ipod. And the gain from my ipod classic is enough to give a juicy sound to sm3v2 (usually i play them with 75-80% of ipod volume). But if amped..i mean a proper amp..that sm64 is realy, really pleasant to hear.
So is it worth to trade your sm3v2 to sm64? I would not say sm64 is a good replacement for sm3v2. But rather it is a compliment product to sm3v2 I suggest for those who want to replace their sm3v2 should have audition first before you decide to let go your sm3v2. To me the sm3v2 still a good iems. It is easier to drive...and it sound good on whatever amps u use or even no amp. not to mention that creamy lush mids that i miss most of the time during my listening with my sm64.