Well, I ordered my FI-BA-SB and hopefully they will ship soon. It will be very interesting to see what FAD has come up with.
I have the 1601SS's already, and must admit to a bit of love/hate with them. They are really upfront with what they do wrong with some noticable tonal deviations, that is, a subdued bass and high treble and an emphesis in the mid-trebles before they roll off. And to even get this level of balance requires very careful selection of tips (for me, the supplied large tips with the radial slots cut in are the best by far). And keeping them in your ears in the right spot is a bit of a task. The eq-7 and ck-10 are both more initially "friendly" and easy to get along with.
But but but...
The 1601SS's have qualities that transcend some of the usual limitations of the IEM's I have heard.
a) The IEM's I have heard all seem to vaguely sound like they are straining to get the music out, especially when things get busy
b) They soundstage small and pretty much "in the head"
c) The sound a bit microdynamically challanged
d) It's harder to hear "into" the music, that is the spaces between instruments
The 1601SS's never seem to run out of steam, keeping the musical threads sorted even when things get busy. You can hear the "spaces" stay clear and the full(er) range of dynamic expressiveness. And the presentation is much more "out of head", more spacious and much closer to a full sized headphone though still well behind the newer angled driver presentations (such as the T-1, HD-800 etc.).
Now fundamentally, their deviations from neutral-ish trouble me, without question. Bit at the same time, the 1601SS bring the limitations of typical IEM's, again, at least the ones I have owned (eq-7, ER4-P, CK-10, HJE-900, Westone UM3, IE-8 etc.) into bold relief.
Sometimes I can't decide whether the 1601SS are a noble mistake or a work of genius. I hope that at least some of their weird magic carries over to the FI-BA-SB...
Kevin