Before I post my initial impressions, I wish to thank my dear friend -y0- for the opportunity.
Let's begin with the earphones themselves. For the sake of this initial impression, I'll be referring to the 2V1S as the '1V', reflective of the name change they're (hopefully) due to undergo at some point. As far as aesthetics are concerned, the 1V's are quite appealing, and of solid construction and build. The cable, while quite thin, feels quite sturdy, and is similar to the cable found on the Sennheiser IE7/IE8 in that regard, albeit thinner. The 1V can be comfortably worn in either a straight-cable, or an over-the-ear fashion. Microphonics are nonexistent when worn over-the-ear, and slightly above average when worn straight-cable. Then there's the one area in which I'm truly disappointed. This current set of 1V's experiences terrible driver flex, and I do mean absolutely terrible. It's only of concern when they're first being worn, after which it's no longer an issue. Having to encounter it each time they're worn, however, is rather irritating, and it may take a few seconds each time to adjust their alignment, so as to not experience any further driver flex. Insert them a tad too deep, and the sound becomes blocked out altogether. Seldom times, a slight opening of the jaw will result in the same sound block. Simply put, there's a learning curve involved before I knew how to properly insert them, but I'm willing to overlook the issue as I'm quite certain the set -y0- received just so happens to be among the unlucky few experiencing significant driver flex, or so I hope.
Now, onto the subject we are all here for, their sound. For my own listening impressions, I wore them over-the-ear, coupled with the large JVC tips that come included with the FXT90/FX700, which (from my experience) offer the best overall transparency. While the topic has been discussed to no end here and elsewhere, I'm forced to reiterate whatever's been said with respect to the low end, especially since it's the very first thing that'll draw the listener's attention, and will most probably remain the focal point of attention, irrespective of track/genre. I don't wish to call these bass-heavy, but before you get up and leave, hear me out. 
If I were to call these bass-heavy, it'd tip the scale to a completely new extreme, and would most probably throw off my perception of all other in-ears I've heard to date, which, before the 1V, I've come to classify as bass-heavy in ears. The DDM2 is a prime example. The 1V is what I'd call the heavily exaggerated counterpart of a bass-heavy earphone. As with everything, there are both pros and cons. Before I say anything, let's get right down to it. These are intended for listeners who want a relatively bass-dominant presentation, particularly bass QUANTITY above all else. I say relatively because I don't wish to say they're completely bass-dominant, and give the false impressions that the mids and highs are not at all prominent, or that they're totally lacking in presence. To my surprise, that's not at all the case. If asked to describe the lower frequency range, I'd say it's weighty, aggressive, seismic, extending quite deep, and (unfortunately) all the while, quite boomy. While they may sound quite muddy/bloated at times, more often than not, the low end retains good definition and overall transparency. Let's face it, the low end is heavily colored, but that shouldn't come to a surprise, since the TFTA's are intended to sound that way in the first place. While there's an abundance of quantity, they aren't necessarily lacking in quality. In fact, the low end is really where the story begins, and (for many) sadly ends.
That brings us to the midrange. Given the overly emphasized midbass and subbass, it's no surprise that the midrange is undoubtedly recessed (more or less, depending on the track). At times, quieter passages are far too recessed to make out clearly. The overall midrange detail, clarity, and transparency are all average at best, though I must admit, slightly better than I expected, considering their overall presentation. As is expected however, more often than not, the bass is much too boomy and prominent, and noticeably infiltrates the midrange. This is most noticeable with vocal tracks, where midbass bleed is quite apparent, and, to an extent, compromises overall clarity and transparency. Nothing short of expected of course, considering (yet again) the intended purpose of the TFTA's, as first and foremost absolute bass cannons. Then there's the rather confusing high end. I say confusing because it appears to be rather smooth, and laid back, yet sounds as if it's constantly competing with the lower end to gain focus/presence. It's hard to pin point, but it's as if the high and low end are tossed into a mixed bag, making it rather difficult to appreciate either one as an individual entity. The weighty lower end is, yet again, the obvious culprit. As hard as I try, it's nearly impossible to draw my attention away from the lower end, leaving much to be desired with regards to the rest of the spectrum.
Imaging and instrument separation, however, are average at best, both of which failed to meet my expectations. It's a rather strange combination, as if they're unable to take full advantage of the pleasantly wide soundstage, similar to that of many vented dynamics. Then again, the UM3X, which happens to be exceptional in that regard, suffers from a rather narrow soundstage, one that I could never quite get used to. In fact, the 1V sounds rather veiled/congested at times. Anyone hoping to use these with genre's that aren't bass heavy, I wholeheartedly recommend you look elsewhere. So who do I feel these are fit for? Well, as has been mentioned here and elsewhere, simply put, those that want a warm and fun brain thumping experience, with the most weightiest low end money can buy, period. Don't be mislead to believe these are intended for any other means. I must admit, I had a rather difficult time tolerating them for longer than a few minutes (but I persisted), especially since I personally strive for a sound with that's closer to neutral than not, with exceptional detail, clarity, and transparency. I personally don't see myself paying retail for these, not now, not ever. However, I don't wish to deter those prospective buyer's who care for little else other than the lower end of the spectrum. In that regard, you won't find a more competent solution, I'd put my money on it. As of now, I'm happy to conclude my brief impression, and let them sit aside for burn-in, after which I'll post back any changes I perceive. 
