Well, depend on what You will compare to. It still has more bass quantity than ba drivers. Fit is their real problem. I'm luck it can fit me ears!
Well I have to agree with yangian, I too really like the UiiSii Hi-905. I will try to describe what I hear from these earphones so you can decide whether they fit your preferences.
First fit was difficult but once I figured it out I found them to be very comfortable. I had to use a larger than normal tip, I usually find the large KZ starline tips work for me but had to use a larger tip with the Hi-905. I insert the earphone with the cable down and twist the bottom up while pushing in a little and stop when the cable is about at the 8 o'clock position, this seem to seat the tip deeper in the ear canal. I then run the cable over my ear. By doing this I was able to get a good seal that produced the best sound.
I would classify the sound signature as balanced and tending towards neutral. Other earphone that I own that I would classify as having a similar signature would be Vivo XE800, Havi B3 Pro. and BYZ K17. As for headphones I would also place the AKG Q701 with this list.
I don't think many people have experience with the BYZ K17 so I will compare the Hi-905s to the XE800 and B3 Pro.
Treble
Like the XE800 the Hi-905 is well extended and provides crisp detailed treble. With the Hi-905 the notes in the treble seem to be a little thicker resulting in a richer sound. I believe some would consider both these on the bright side and I did have to burn in the XE800 for over 400 hrs. to get the treble to where I like it and I think I am quite treble tolerant. On occasion I notice the XE800 to be sibilant but I have not noticed this with the Hi-905.
I find that the treble on the B3 Pro is not quite as extend and although it is detailed it lacks the crispness of the XE800 and Hi-905. The B3 Pro would be the best choice of the three for anyone who is treble sensitive.
Bass
As far as bass the Hi-905 is very similar to the tight punchy bass of the XE800 however the Hi-905 has more sub bass.
The bass on the B3 Pro is not as tight or punchy as either of the other two. I find that the amount of bass is very similar on all three but I prefer the punchier bass on the XE800 and Hi-905
Mids
All three of these earphones do a good job on the mids and as say I find them to balanced so the mids are not forward or recessed.
Sound stage,
The B3 Pro is known for a wide sound stage and I find that the Hi-905 equals the width of the B3 Pros sound stage. Both these earphones have a wider sound stage than the XE800.
What sets the Hi-905 apart is in the positioning of instruments they have height, layering and a forward dimension. 1clearhead referred to this as a holographic effect and what I find it does is provide a sense of space and openness that I have not found with any of my other earphone.
So if you like big extended bass, then yes, you will find the bass on the Hi-905 lacking. If you are treble sensitive you will probably find the Hi-905 bright. If you prefer a balanced earphone that is neutral, you will likely like the Hi-905. If you are like me and are looking for a headphone that has something that sets it apart from the others in your collection, then the holographic effect might be that something.
I have been using the Hi-905s for over a month now and like them more and more with each listening session. Do I like to throw on a bassier pair periodically, yes I do, but I find the Hi-905s best suit my preferred sound signature.