SIGNATURE

The FDX1 on stock filters (AKA FD01) can be considered as “Harman-neutral” as it follows the Diffuse Field upper-midrange emphasis somewhat with a boosted bass response, though not to the level of “true Harman”.

The green and blue filters simply sound neutral with the aforementioned sub-bass emphasis. Mid-bass presence is not very pronounced and most of the bass’ weight comes from rumble rather than punch.

THE “BAD”

The FDX1 is a lean sounding monitor. Not necessarily a bad thing; the lesser mid-bass and lower-midrange response helps with highlighting the sub-bass and is part of the reason why the bass sounds as controlled as it is. Unfortunately this means that the FDX1 is not an IEM I would describe as “rich”, “smooth” or even “musical”, whatever that’s supposed to mean. The FDX1 is not an IEM I’d reach for when I’m feeling like listening to Sinatra or some of my cello-heavy orchestral tracks for instance, not really conveying the sense of weight in the notes that these tracks require for my definition of the full experience. Imaging is also average in the grand scheme of things, with neither the soundstage size nor positional cues impressing me. Again though, something like 80% of IEMs have “average imaging” to me so this isn’t really a problem for me or most people.

A minor nitpick from a timbral standpoint: the decay could use just a little bit more linger. Just some extra reverb to put some meat on those bones, but it’s really a very minor criticism that I can happily do without. Though if that happened, it would certainly justify a rank upgrade…

THE GOOD

With many Harman-tuned IEMs, I find myself making excuses for my enjoyment of the signature, or more specifically why I should be enjoying myself. Statements like “despite the upper-midrange emphasis” start to pop up, and the inevitable arguments about why I’m Satan for not agreeing with Harman’s research come in.

With the FDX1 there are no excuses; the pinna gain is tuned to my desired magnitude and pattern, the bass is boosted properly with zero bleed or smearing, and treble still retains sparkle and energy without being anywhere close to sibilance or harshness. From a tonal perspective, it’s as good as it gets (for my own ears).

And of course, let’s talk technicalities. Decently quick attack and lightning fast decay results in a very detail-forward and well-defined sound. And yet, despite the transients that are almost unnatural for a DD IEM, the basslines still retain its authority and impact without any diminishment common with BA woofers. Sub-bass still comes in with plenty of rumble and weight, with the weight reducing as the drivers approach the mid-bass frequencies and higher. Yet, and this is probably my anti-BA bias talking here, even the quick bass hits of the FDX1 sound more natural than the best pure-BA IEMs I’ve heard.

CONCLUSION

The FDX1 is an amazing “technical DD” chock full of all the subjective goodies that many experienced ears hold dear, yet exquistely tuned to highlight just the right parts without offending the sensibilities of the average audiophile. Its reputation even in its early days as a mod is well-justified, and it is one hell of a blessing to have this mod now available as its own standalone product.

No doubt in my mind here, the FDX1 absolutely deserves to be the cheapest IEM in its tier right now.