Sorry to late!
After 1week burn-in and listening various music, sounds, and test tones carefully, I made up the following impression on the SIGNA UIEM.
When I checked all IEMs in late night due to outside noise and stability of power line even Japan's power line quality is one of best in the world.
Therefore it requires more time.
I changed ear piece to the SendnaEarfit XELASTEC and 4 core pure silver (and tried with 8 core pure silver).
TEAC's headphone amp.
1. Sub-bass and Bass: Rich and enough + well controlled. I could hear (feel) <20Hz (actually 11-12Hz) -- not sound, it's a vibration and pressure by wind like.
It must help to reproduce sound stage better than FE3U even the frequency performance specification of both SINGA and FE3U is exactly the same. 15Hz-22KHz..
There is no concrete condition on such spec, though. -- it's common and a difficult point. The frequency response doe's not show all performance of product.
2. Middle: no explanation is needed. -- GOOD and smooth.
3. High: Felt narrower distribution of frequency response than FE2U which has a bit large peak around 9KHz which may help to cause harsh...
Gradually decreased as higher frequency and it helps to provide natural sound.
Fe3U looks to have more extended output in higher frequency than SINGA, however, FE3U tends to add distorted sound in such high frequency area due to peak. The SINGA looks to provide smooth sound with lower distortion (than FE3U) and some customers would feel a bit lower energy in such high area.
I think it depends on which or what sound the customers proffer, though, from pure and less distortion sound point of view, I like SIGNA rather than FE3U -- if I should be asked to pick up between SIGNA and FE3U. FE3U looks to be more aggressive than SIGNA.
---- my ear is not so good and I think I can hear up to 12KHz (-0.5,+1KHz -- depends on my condition).
4. SINGA provides better natural sound and sound stage --- I believe dual use of each BA can support lower distortion even higher output. FE3U has single for each frequency bandwith,
5. Hisenior's B6+, Fe3U, and SINGA is monitor like sound performance and even each has different character.
I can enjoy with them. Basically I prefer monitor like performance since I was supporting sound recording when I was student as my hobby.
B6+: Flat and natural but lower bandwidth
FE3U: Wider range and a bit harsh at some peaks. -- aggressive.
SINGA: Rich soundstage and natural. Lower distortion.
6.. Problem (just in my case -:) )
Lower distortion and tending not add modulation noise, distortion product may easily to let me listen with higher power, louder .... I need to be carefull.
I am not audio file but I already introduced Hisensor to my friends as very good and honest IEM company.
( When the COVID issue will be over, I will visit my heath doctor to try my IEMs--- I promised, but still early).
I am sorry again I don't put my comment on you link. I trust you and your company.