My HTFs are on their way to their next owner. I got a chance to compare them to a pair of new-to-me JVC HA-RX700s briefly this morning before I shipped them out. The RX700s definitely beat the pants off the RX500s. They are also the closest phone I currently have to the HTF's sonic signature, and they are quite close in terms of current going price.
Brief synopsis:
RX700:
- Seems fuller / bigger / fatter than the HTFs in the 40-60Hz region, but not quite as happy way down in the 30s as the HTFs; so, depending on what you're listening to, sounds either bassier *or* thinner than the HTFs
- Smoother integration of bass register with low mids
- Slightly recessed / scooped compared to the HTFs in the ~2000-4000Hz range; voice seems SLIGHTLY subdued by comparison on SOME recordings
- Markedly better ultra-high response (but still not a bright phone)
- Snare drums are punchier, cymbals are crisper - noticeably, but not exactly leaps and bounds
- Soundstage is markedly wider
- Slightly harder to push
- Much more revealing of bad encoding; still quite forgiving of bad recordings (maybe more so than the HTFs, actually, as borne out by some old indie-rock album tests)
- Closed can; no leaky-leaky.
HTF600:
- Better response in the almost-lowest recessses of bassland than the RX700
- Slightly richer low mids
- Slightly less punch with percussion and transients
- Boxier, flatter soundstage
- Upper mids sound just a tad "honky" / "plasticky" in side-by-side comparison to the 700s
- Sounds better with badly-encoded / -compressed sources
Fashionistas would probably be happier with the HTF in public due to its smaller on-head / on-ear profile-- although their neighbors on the train or plane definitely would be happier with the totally-closed RX700s.
Tough call at the current price for the HTFs... they are similar-sounding cans to my ear in a lot of ways. I would not use either one for mission-critical monitoring, but they're both pretty fun phones to listen to.