The robust build quality of the IV-4S got me interested to try them. Unfortunately, I received a defective pair. Judging by the right channel (the faultless one), the bass is mostly distorted while vocals sound harsh and shouty. I wouldn't recommend these earphones to anyone, unless I hate them very much.
Again, this is a sad occasion where you get a very unique build quality, but poor sound quality.
Soft paperboard
S+M+L, grey (translucent), ø5mm red bores
Faux foam, red, ø4mm bores
White, 360° cable holder, generic
Leatherette, black, branded
Metal, ø5mm nozzles, soft strain reliefs
Metal, single-button
Metal, no strain reliefs
Silicone-coated (smooth), soft, mildly bent
Metal, straight, short, no strain relief
They fit really good with the pre-applied tips. They aren't bulky and don't fall out easily.
For the defective pair I received, I can only say that the bass is present, but is very poor and distorted.
The vocals are somewhat quiet, but from what I can gather, they seem to sound quite decent. Slightly harsh, slightly sibilant, but overall not that bad.
There's a noticeable peak on the defective channel that cause huge sibilance. That probably doesn't happen on a properly working pair. Judging solely by the non-defective right channel, the highs seem a bit harsh but overall decent.
