All of the wooden JVC IEMs have way too much bass and sound congested in the low range when compared to better balanced phones. However, if you compare treble, you'll see that detail resolution in the highs is very competitive. That means the JVC drivers aren't inferior per se, but the tuning makes them sound inferior.
I've posted instructions in the FX850 threads on how these (and the FX1100) can be modified to drastically improve their tuning. To my ears, the modified FX850 and FX1100 sound easily as good as my K3003, if not better.
Unscrew the brass back plug:
Insert cotton into the chamber and tune the bass.
Unscrew the back brass plug and open the body, insert cotton into the chamber. I can unscrew it with my fingers, this avoids damaging the brass plug. You can fine tune the bass amount and characteristics to certain degree, it is easier and more controllable than the straw method. The more cotton I put in there, the amount of bass is reduced and the mid-high portion of the sound spectrum will be more forward. This does not change the basic sound characteristics, but musically, I can feel the difference. When I fill it and push the cotton tight inside, the bass is a little bit less than what I would like, but still very present, at the end of several try and error, I put enough cotton inside to fill about 1/2 of the chamber. Screw it back then there you go. Nice and easy, no harm can be done there. I have not try other type of materials since cotton is handy and I use it to tune my speakers all the time, the results are very acceptable. You can find the front portion of the chamber is already filled with cotton anyway. This method can be applied to FX1100/1200 also.
I use mostly live recordings to get the right feel of the sound in the tuning process.
I have not tried but I think I can completely block the vent if I want to, but I don't know if that is what I want.
To my feeling, it is like tuning the bass characteristics in the bass reflect speaker boxes by filling materials inside.
This is fun because now I can easily tuning the sound stage, presence and bass characteristics.
Does not hurt to try, since you can always take the cotton you inside and put the plug back, undo all changes, not hurt can be done.
This is a really nice IEM, the basic sound characteristics are great, that makes the tuning more fun.
I am listening to my end results now and I really enjoys the sound going into my ears now, just the right amount of everything...
Best part, you cannot void the warranty since it can be undone and no traces are there, ha ha.
