I manage to get a good listen to the FW01, 02 and 03. Just a few notes:
FW03's body looks to be smaller in size compared to the 02 and 01, I think the 02 and 01 are the same in time but I didn't do a side-by-side comparison. These guys are huge, probably the same size as the FX series.
As the nozzles are angled, you can only wear them hanging down. And due to their huge sizes, I can foresee them breaking seal or dropping out of my ears easily due to their weight.
The 01 and 02 have removable cables with mmcx plugs, the 03 are non removable.
I've listened to the FX series when they were first released, and that is a long time ago so my sonic memory of them are rusty. However, my general impressions are the same as those above:
(btw, I listened to these with my Sony hybrid tips instead of the default tips because it sounds better on my Sony tips. I suspect they will sound even better with the JVC spiral tips.)
I was pleasantly surprised when I first tried the FW03. I was expecting the typical JVC V shaped sound signature, and warm due to the wood body, like the FX series. While these still have the V shaped sound (heavy bass and great trebles), there is less coloration and less warmth compared to the FX series.
The FW03 is probably the most polite sounding of the 3, with some roll off in the bass and treble regions, hence making it sound more “reference" than the rest. But it doesn't sound like a DD earphones without the subbass.
The FW02 is like the opposite, with the bass and the treble turned way up high. While it was initially addictive head banging to it, it does get fatiguing awfully quick.
The FW01 is undoubtedly the best of the three. It has bass and treble, but controlled unlike the FW02. Many people will probably still find the bass to be too strong, but if you like the JVC sound signature, you won't be bothered by the bass. In fact, you'll probably love it.