This and That:
Lots of included accessories. Lots of different nozzles (generally two categories: hollow and damped nozzles).
Build quality is quite decent but the in-ear looks rather like a cheap one. That the collared 2-pin connector joints appear somewhat like a weak spot doesn't help either.
Very decent twisted cable (the one with the microphone is however quite disappointing in terms of suppleness).
Sound:
I'm only using low impedance sources (clearly less than 1 Ohm) as well as the largest included single-flange silicone tips. Because of the in-ear's shape, I'm inserting the ear pieces slightly deeper.
Tuning:
To me, the hollow nozzles are basically junk as their midrange reproduction is very hollow and reverberant due to a bright upper midrange and central treble lift along with a lift in the upper highs. The bass ranges from more or less mild (purple) to very strong (silver; ca. 16 dB more bass compared to a diffuse-field flat Etymotic ER-4S/ER4SR low-end).
The damped filters are much better in this regard and render a fairly accurate midrange that is balanced with some warmth in the fundamentals and a very mild lift around 3.5 kHz. As a result, the midrange sounds fairly natural.
The highs are in the back around 5 kHz where they sound dark and come back with a 9 kHz lift that's not narrow. It's only slightly bright, but it isn't sharp and only slightly above neutral and not really obtrusive, even though it leads to cymbals sounding a bit sizzly.
The lows' emphasis is the strongest with the silver ones and the mildest with the purple ones, just like with the hollow ones. The ones I personally like most are the purple ones as they are the least bassy. Nonetheless the fundamentals are still fairly full sounding with them and the lows are still undeniably on the warm side. The emphasis is generally more on the fundamentals and upper tail of the upper bass around 200 than on the midbass, with a moderate roll-off towards the sub-bass. The upper bass carries around 5, 6 dB more quantity compared to an in-ear with a diffuse-field bass but appears omnipresent and subjectively stronger, fuller, which is also partially caused by the rather poor bass quality.
Resolution:
The resolution is somewhat disappointing.
The bass is quite soft, slow and also somewhat foggy, leading to it lingering what makes it sound fuller and stronger than it actually is. It just sounds muddy if the track is only somewhat complex. It even appears a bit slower and softer than that of my Sennheiser IE 80, an in-ear that isn't known for tightness and speed either.
Treble and midrange details aren't overwhelming either. The separation is okay and one might notice that the Delta V-II is using a BA driver, however once the track is busy or more complex, the details aren't really there as they should. Most single-BA in-ears perform better for less.
Soundstage:
The soundstage is okay but could be more precise. Generally a bit foggy when it comes to instrument separation.
Not particularly bad but not especially good either. Just average.
Fortunately fairly circular and therefore three-dimensional.
Conclusion:
Many filters but only few of them are actually useful while about half of them sound hollow and reverberant. Thick appearing upper bass and low fundamental range. Poor bass quality (soft, spongy, slow). Only average midrange and treble resolution; separation not very sharp. Soundstage circular but rather foggy.