My thoughts on: Etymotic ER2XR & ER2SE
Etymotic utilizes dynamic drivers in the ER2 series compared to balanced armature drivers in the ER3 and ER4. I bought these just because they were DD (lol).
ER2XR
The ER2XR has a smooth, easy to listen, downslope type of FR. It actually features quite a big bass boost relative to the diffuse curve. Warm tone thats highly pleasing. I dont find the midbass bloated at all, and actually think the bass boost is very much well implemented here. Subbass reaches low with nicely defined basslines. Midrange sounds...DF-like with more warmth. Due to the smoothness of the signature it does miss out on some detail at the midrange. Lower treble is where I find that it has its issue - I do think the lower treble is quite recessed when compared to everywhere else. Treble is dark sounding to me and lacking of more presence in the 5-8kHz region. Upper treble does extend ok. But due to this recession in the lower treble (for my preferences), the treble can sound hazy and too laidback overall. Staging wise I dont feel that they congest. Things layer upon themselves well. Just sounds more in-your-head when compared to regular iems. If you've heard Etys before, it's that same kind of staging, perhaps a bit bigger. Maybe they positioned the driver further away from the nozzle. I dont exactly know. I felt that soundstage was less of an issue when compared to ER3.
ER2SE
Very similar but with less bass. The deepest subbass registers can still be heard faintly, but lacks presence for me. Due to there being less bass, the tonal balance shifts more towards the uppermids and treble. Its in an odd spot where I'm content with the uppermids/treble but lacks that subbass. Midbass is of lesser quantity but sounds tighter as it should be.
The dynamic drivers seem to be quite capable in the ER2 series. They are very fast and snappy but due to their nature of their smoothness, they seem to lack that resolve when compared to ER4. That said, I recommend them. They are hard to fault outside of the usual "ety soundstage" issue. If you haven't tried Etymotics, maybe start with these. But even if you own the ER4, I think these are also nice to have around - they are smoother and offer an easier listening experience.
edit: since people have been asking me about these vs ex800st, I feel ex800st holds the same level of resolve. Ety also offers some of the best isolation you can get. EX800st just does staging better but trades off isolation.