Bass: There is a nice presence of bass overall. The bass transient response isn't too great however. The amount of mid-bass is almost perfect to me. Not too much, not too little. The sub-bass has got a nice impact to it but just not as strong and impressive as on my Turbines. The bass overall has good speed and does not bleed into the mids at all. The bass could be tighter though. Kick-drums sound impactful and have got nice thump. My Fiio E7 does help these IEMs by broadening the bass presence. When on-the-go, the small boost in mid-bass helps to keep the warm sound signature of these IEMs, especially in noisy environments such as on the bus.
Mids: The mids are nicely articulated, handling complex passages well. There is great texture to both the mids and upper mids. The vocals don't sound too impressive nevertheless. They are just "there". The "s" and the "t" sounds do sound accentuated but not to a point where it’s too annoying. This gives the vocals a ghostlike feel nonetheless. I would have preferred fuller and warmer vocals. Acoustic guitars sound very beautiful I have to admit. The transient response of the mids with the acoustic guitar is just amazing. They do sound a tad "artificial" though. The upper mids sound clear and articulated, electric guitar solos shine very well. However, they have a metallic feel to them that could be a little bit annoying.
Treble: Shimmers, great level of detail. Metallic-sounding. A small amount of sibilance is often present. I have never heard cymbals so clear before. It has quite a large amount of brilliance. I could say that it is quite coloured although I do not know the exact definition of a "coloured" treble.
Soundstage: Oddly-shaped, slightly circular. Not too large. The instruments however seem to be nicely positioned, each separated from another. There is a resonance that is apparent mostly on the quiter tracks.
They are very revealing. I can hear the poor mastering and distortion on some tracks, which is to be expected with metal songs. The instrument separation is excellent. Even in the most complex passages, the instruments are discernible from each other. They are very fast. Great attack, a good amount of decay. Imaging is near excellent.
In conclusion, these are the best IEMs I have ever owned and are pretty solid at their price point. Although the bass could have been tighter and more defined, the sound quality of the XBA-3s is near perfect IMO for a pair of universal IEMs. Despite this fact, they have given me a thirst for more and the excitement of discovering even better IEMs.