Re' Bass of T-F10 vs. ACH-700, it's not that the T-F10s don't have bass response, it's just that the ACH-700s have far 'rounder' bass than the T-F10s, and more satisfying, to my ears (e.g. James Taylor's track 'Gaia' comes across with a slightly greater sense of 'scale' with the ACH-700s and much better timbre). Neither the T-F10 or the ACH-700 has perfect bass, however.
But regarding the treble, it's not so much that I'd use the word 'sibilant' (although I don't actually disagree with that term in relation to the T-F10s) - personally, it's more that the treble just sounds fake; conspicuously and incongruously superimposed upon the frequencies lower down the spectrum. It's not at all convincing and, personally, I feel it's downright outrageous that this IEM is marketed, with this synthetic-sounding treble, at anything over $80. I'm also intrigued that a quick check of UE's website (USA version) does NOT (at time of this writing) list the T-F10 as a current product, although it is listed on the Aus and UK regions of UE's website. You can draw your own conclusions about why that might be.
A particularly noticable example of the unrealistic and intrusive tweeter on the T-F10 is when listening to female vocals with lots of upper midband crossing-over into the treble domain. Perfect example of this is Alison Krauss. Properly portrayed, her voice is astonishingly pure, but played through the T-F10s, there is a treble 'rasping' to her vocals which is totally unwarranted and totally unacceptable. I was listening to this just a couple of hours ago, before I packaged the T-F10s for return to Amazon. I was shaking my head in disbelief - why is such blatant treble colouration even there, since this is from supposed experts in BA IEM design and production?
In truth, I'm past caring now. I'm glad I purchased via Amazon, since their cutomer service is top-notch.
All the best to those of you who enjoy the T-F10, but I'm scratching my head in bewilderment as to why you do..!
Edited by Mython - 1/2/12 at 1:53pm