Thank you for making me go back to the FXH30 for some serious listening. I've been spending all my time with the KZ ZS1, HDS1 and ED3c since they arrived a couple week ago.
I can't agree with those observations at all, mind you I'm comparing to the 60/80, not the 70, and do not use the stock tips. Wide bore tips are an absolute necessity with the FXH30. The stock tips hold them back considerably. I've also got at least a couple hundred hours or more on them by now.
Yes the FXH30 has greater bass emphasis (midbass most notably), but it is exceptionally quick, nimble, and unlike the FXDs is there in more realistic quantities with live music. They're close I guess, but the FXDs lack the texture and control of the FXH30.
The FXD series iems are also extremely thin in the treble and mids. This is a nice trick for enhancing detail and making them sound more spacious and accurate, but it's just a trick. The FXH30 keeps that detail, has a similarly sized soundstage (ie. not large), greater depth and outstandingly well defined layers, and adds much needed weight and thickness making them sound immeasurably more natural and realistic.
The largest improvement over the FXDs is in their timbre and texture, and smoothing out that painful treble (something JVC has done for many of their current-gen iems). Listening to an orchestra for example, I find it's noticeably easier to pick out and listen to individual instruments. With the FXDs the emphasis is so focused on the razer sharp treble and upper mids that deeper instruments just get overshadowed and lost. There is also that metallic edge they put on everything. Very uncomfortable, especially with metal and thrash in particular. Thrown on some Vortex or Thrashfire (https://www.youtube.com/watch?v=BVimw69CL9Q) and the FXDs become a bit of a mess. With the FXH everything is still well-defined, drums actually have some kick and realistic decay, and vocals have some breadth and weight. The FXH30 can handle some seriously busy and dynamic music with ease. There is a reason they got me back into metal. Nothing I own, especially the FXDs, comes close to handling it as competently as the FXH30. I imagine the FXH20 would be even better for metal given their reduced bass, though crunchy electric guitar riffs sounds f'ing phenomenal with the FXH30.
The biggest knock I have against the FXD series is just how thin they sound. There's just no weight to them. The brightness I can work with.
The FXH30 would benefit from a wider and taller soundstage.
@yacobx The FXH30 do not lack subbass at all. I love my deep, obscenely rumbly subbass (KZ ZS1 is amazing for this!), and never feel like the FXH30 needs more. More is always better, but not needed in this case
All of this is my opinion of course, and I completely respect yours @Sweden, but outside of better build quality the FXD series feels a bit weightless next to their successor. I just can't see any situation where I'd recommend an FXD over the FXH.
Its obvious that you have a special place in your hear for the fxh, I guess one of the other turn offs for me is the design of the headphone. I wear all my earphones over my ears and i dont think its possible with those.