I would say Hifiman R10 (either dynamic or planar version) has no relationship with original R10 at all. Not to mention the cheap $5 woodcup, the sound is not similar to original at all. Hifiman do make good headphones like Susvara and HD1000 etc, but the R10 series is a joke and they are so overpriced.
ESR10 on the other hand, is trying to achieve the original sound of SONY R10. I wouldn’t say it 100% achieved that but at least their tuning style is so similar and the difference is marginal without a very good amp. I can’t tell the difference when using the headphone jack of WEISS DAC202, but when I use EC Studio B with HE1 preamp the difference is noticeable. But still they sounds quite similar.
I think hifimans own marketing on there site shows where they are coming from. There is a frequency response picture for the he-r10d with a line that reads "respect the classic model and surpass its performance."
On the other hand though I remember reading texts quoting him in the conference video (which I can't find the video any more) revealing the he-r10 headphones and saying things like
"43:30 - Bian says Sony R10 is not as good as people claims it to be. He prefers Bose NC700, Sony XB900N and Sony WH-1000XM3 over Sony R10.
49:30 - Bian addresses the haters, "I know people out there will accuse us of copying Sony. This product is not paying homage to Sony ('s design). Sony and I are competitors. Homage or not, all we (Hifiman and Sony) should care about is making good product. Even though Sony owns more market share, you (Sony) won't be able to sue me. I researched Sony's patents; they are expired. (Audience applaud in laughter)""
So I got mixed messages on what the he-r10d is exactly and after finally hearing it I think it is actually well, a lazy attempt to "respect the classic model and surpass its performance." If that is the he-r10d's goal then it failed at doing just that. I stand by my view that it is making an attempt to be a better modernized r10 (on paper anyway). The problem is, Bian Fang set a pretty ambitious goal that in the end could not be realized.
A person who talks a big game needs to back it up with proof and when hifiman finally released the he-r10d and I got to hear it myself with my es-r10, while I can understand the direction they were going for, to say this surpasses an r10 (in my case es-r10), well let's just say I've noticed hifiman has not really spoken of this product since and have moved on the he-r9.
Now I don't know all the complex decisions that would go into making a headphone, but I would guess that if you want to make a better r10, you
absolutely cannot compromise on the quality of parts that could help in optimizing the driver. Like take a stradivarius violin for example. Sure you could use today's advance sciences to come up with a modern copy to an interesting effect, and to an untrained ear maybe they might have trouble figuring out which is which, but to more discerning ears like folks here and on other audiophile sites, we are not so easily fooled. Aspects of the he-r10d might remind me of my es-r10, but in the end for me the he-r10d was less of a stradivarius (es-r10), and more like Fischer prices interpretation of a stradivarius.
So you are right rzy6cn, they are not a one to one copy, but a failed
reinterpretation of the r10.