thought i could post some early impressions.
fit and comfort: the design is pretty much the same as the Crystal's, so a big plus in my book as i liked those quite a lot. among the most comfortable ones i tried.
isolation is decent, but nothing outstanding.
as for the sound. still not sure, but overall they have a flat response. nice extension on both ends. sparkly highs (a tad rolled-off). good bass for a small single BA. clear mids, but lacking warmth. for the moment i can say these are not really meant for vocals. even the DBA02/B2 have a fuller midrange
soundstage is quite good though.
the tips 2 position makes a drastic change. place them up to the end and you get a thicker/richer and more intimate sound, but smaller stage.
with tips at the front: spacious sound and wider stage. more air and better separation. but softer on bass.
for those who asked a RE-400 comparision:
they very very different. first, the re400 wins hands down on midrange and specially on vocals. the hifiman have one of the most beautiful mids.
bass quantity is similar. the ba100 are faster (as a BA), but the re400 have more substantial and rumbly sub-bass (as a DD).
highs: smoother on the re400, while more sparkly on the ba100 (yet sibilant free)
ba100 wins on speed and stage
details: a tie
on their own, the HSA Ba100 are quite good but need some more time to appreciate them. and personally i'm quite impressed. well done HSA for your first BA release!
that's for now. sorry for the messed language, but these are just some first impressions
I haven't heard the RE-400 so certainly can't comment on the comparison but if you have some TF10 type double flanges to try, pushed all the way down the nozzle, see what you think. I've heard good things about Meelctronics balanced sound doubles but have no idea if they would be a good match as well. I suspect there's someone with a set of these that will have BA100s and can report.