Interesting finding: I was listening back-and-forth between about 6-8 different IEMs, and the TinHifi T4 seemed tuned closest to my Edifier 1280T desktop speaker.
Both in terms of tone/timbre and soundstage, T4 was unusually close to the 1280T.
The other IEMs did not have the same timbre. In comparison to the BLONs, HZSound Heart Mirror, EDX, and Starsea, the T4 sounded 'sweetest,' and it obviously wasn't as bassy as the BLONs.
The T4 provides a pleasant warm-neutral timbre, and a soundstage that carefully separates the elements across the width. For some genres, that is just what you're looking for.
I now see what people mean by the T4's "average" soundstage. I had been critical of it, but it's okay. Just not as wide as the Edifier desktop speakers provide. The BL-01 sounds more 'closed in' for sure. Good directionality, but the BL-01 is 'closed in.' [Starsea has a greater soundstage.]
T2+ vs T4 Timbre
I also listened to the T2+, and I think the T2+ had a more sterile tuning. Like people say, it's very safe, but lacks the 'sweetness' of the T4.
So I have to agree with those who said the T4 is better tuned than the T2+, even though the T2+ is reasonable and inoffensive. T4 is just livelier.
TinHifi could make a "T4 Plus" that's simply a T4 in the T2+ housing. T4 has great sound and doesn't need changing, but it needs a new housing.
So what's with the tuning? Was T4 "Harman target?" Are the Edifiers also? I'm now interested in what their tuning goal was.