Sound:
I'm not quite sure if the FA-3E is a two or two and a half way in-ear (I read the latter some time ago), i.e. if there are one or one and a half bass paths (in which case one of the drivers would play a bit higher than the other due to the crossover configuration, while both drivers are identical in construction and not limited at the bottom), but this is largely irrelevant, because it's the implementation that determines how well the end result works.
I've only used my FA-3E on low impedance source devices that don't have any bass drop caused by wrongly dimensioned coupling capacitors in the signal path. Devices that I've used are my beloved iBasso DX90, which is my main source, my SanDisk Sansa Clip Zip, my iPhone 4, the LH Labs Geek Out IEM 100, Cowon Plenue 2, and certainly others.
As for the ear tips, I've always used the largest silicone tips that come with my FA-3E.
Tonality:
The FA-3E is a fairly neutrally tuned in-ear, reminiscent of the UERM in tonal terms, but with a slightly lesser level in the mid-treble and presence range, but (fortunately) without the pronounced peak in the transition from the upper treble to the super-treble as it can be found in Ultimate Ears' in-ear. Accordingly, it doesn't sound sharp or harsh in the upper treble.
Accordingly, it doesn't sound sharp or pointed in the upper tweeter, which is unfortunately the case with my UERM when a note hits exactly this frequency.
The bass range of the FA-3E is even and flat from the lower fundamental to the sub-bass, without any roll-off, and has between 3 and 4 dB more level than an in-ear with a diffuse-field neutral bass range such as my Etymotic ER-4S or the ER4SR.
Thus the bass range of the Fischer Amps in-ear has the same quantity as my UERM, Shure SE425 or the Noble SAVANNA, all of them also quite neutral representatives of their class, but contrary to my Shure and the Noble, the bass range of my Fischer Amps in-ear doesn't roll off towards the sub-bass but keeps the same level in the sub-bass as in the upper bass.
The midrange of the FA-3E is tonally correct, without any coloration and not in the foreground foreground, but rather a little bit relaxed, but not seemingly recessed, which is mainly due to a decrease in the mid-treble around 5 kHz, which makes the vocal range appear a little more "relaxed" and less "in the foreground".
On top of that, the upper treble is neutral again and has no unevenness or sudden narrow peaks.
In general, the FA-3E has a very good tonal tuning that is quite neutral, but not exhausting or overwhelming, and offers a good long term sound quality due to the depression in the central treble.
Since there are no sudden narrow dips or peaks, the sound is also realistic and authentic, which is not entirely true for the more expensive and otherwise technically clearly better UERM, which the FA-3E may have had as a reference, because in case of the UERM, the upper treble appears rather artificial and sometimes a little metallic. No, here the FA3E is more like the Noble SAVANNA or Etymotic's ER-4 line, at least in terms of frequency evenness.
Resolution:
If I didn't know that the two bass drivers are back-vented, I don't think I'd hear it, because the bass of the FA-3E is remarkably tight, fast and precise, as it should be for Balanced Armature drivers - the low to moderate softness and "slowness" (compared to very fast closed BA implementations), because in-ears with "back-vented" BA basses are usually of better quality than most in-ears with dynamic bass drivers (with only a few exceptions in the dynamic and hybrid domain)), which is audible on some back-vented BA implementations (e.g. for example, on my InEar StageDiver SD-2 or Fischer Amps FA-4E XB), is thankfully not present on the FA-3E.
Only if you know it, and in a direct comparison, you can sense a minimal "softness" in bass impact, but this can also be present in some other in-ears with large, but non-vented BA drivers in the bass range.
The detail retrieval is reasonable and good for the price, and even if it is "only" upper mid-range compared to some more expensive in-ears like my Logitech/Ultimate Ears UE900 or the Noble Audio SAVANNA, the resolution distribution of the FA-3E is very even and coherent, so there is no area where you could say it is better or worse than another.
And this is exactly what I see as a big advantage in Fischer Amps' in-ear, because there is no area where it shows a weakness - for example, the overall slightly better resolving UE900, SAVANNA and UERM either resolve somewhat less in the mids than in the other areas, roll off a bit towards the sub-bass, or have a not quite authentic, slightly sharp and metallic treble.
Spatial Presentation:
Again, the FA-3E doesn't show any weakness - even though it's not necessarily the best in-ear up to $450, it doesn't sound unpleasantly flat or constricted, but has a stage that is more or less average to slightly bigger than that, and shows a relatively open and quite authentic, although not fully three-dimensional or impressively large room.
Also the stage is quite circular in my ears, with only a little more width than depth.
Instrument separation and location are average (compared to the very best in-ears), without being negatively noticeable, just lacking in exactly representing "emptiness". For the price range this is absolutely good though, and the FA-3E surpasses a few other models, although it doesn't come close to the spatial plasticity and separation and imaging accuracy of secret tips such my the cheaper Pai Audio MR3 or similarly priced but more fun tuned Audio Technica ATH-IM03.
Conclusion:
The Fischer Amps FA-3E is a fantastic in-ear - its rather neutral, but not fatiguing tonal tuning is done extremely successfully and for the price range its detail resolution is good, with convincingly fast, precise and tight bass. In addition, its housings are ergonomically shaped and sit securely in the wearer's ears.
In some areas there are in-ears that may have a bit more resolution in the midrange, an even more convincing soundstage, instrument separation or representation of spatial emptiness, but it is very difficult to impossible to find all of this paired with the tonal balance/neutrality below $500.
As a complete package the FA-3E is very convincing and is therefore still one of my personal favourites for portable use when I am looking for a quite neutral tonal tuning, which is usually the case.