Hmm, well the A4 sounds quite a bit different from the A3/A2S:
- Treble is much less subdued
- With some filter combinations, the can sound V-Shaped (Blue/Gold; Blue/Red)
- Mids are slightly recessed compared to the A3.
- Bass impact is much bigger on the A4
- Seperation and "Blackness" is quite a bit improved
- Soundstage is not that big though, actually feels a bit lacking, especially in depth
The A4 is definitely a bit of a department from the ultra-smooth, downsloping signatures from previous iterations.
Also, after the Easy Earphones disaster, I'm not going to buy the DQSM or similar anytime soon. (Maybe the VT Audio 3+1, but that I will do that on Taobao, a CIEM for sub 250$!)
But after hearing some complains about sibilance, I can assure you that the A4 never, ever, sounded fatiguing or sibilant.