Firstly, before anything else, I have to apologise for my excessive wordiness. I can assure you that in person I’m a man of few words - in fact I’m positively antisocial! I have been an enthusiastic headphone user now for many many years and have seen some remarkable advances in this field as time has gone on. In the last couple of years I have kinda focussed on bluetooth audio and have ended up with some very impressive hardware - the Sony WH1000XM2 and WF1000XM3’s, the Lypertek Tevi, the Apple Airpods and the Mavin Air-X in particular. All of these bluetooth headphones impress me with their sound quality and features - so it’s going to be an interesting experience going back to wired IEM’s after using wireless so often recently.
My current wired IEM’s consist of the Ultimate Ears Triple Fi 10 and Magaosi K3 Pro’s. Playback electronics include the Samsung Galaxy Note 8, AgpTek H1, Acer Chromebook and occasionally the Benjie S5. Additionally I also have the Topping NX2 DAC/Amp and the Nexum Aqua + Bluetooth amplifier. In the past I have owned the Etymotic ER4P, Shure E500 and 1More Triple Driver IEM’s. Most of my music is high-bitrate MP3’s and occasionally some FLAC files. I’m 58 years old - so please take this into account when I talk about sound quality.
Fiio has a reputation for producing some truly excellent audio equipment. Their MP3 players have an enthusiastic following and their multi-driver IEM’s get a lot of positive comments on this site. I personally haven’t had the chance to try out any of Fiio’s products up to now so I was very keen on trying out the FD1’s. When I first read about the specifications for the FD1 I was somewhat dubious about the single driver - when compared against the might of multiple balanced armature drivers and the many hybrid BA/DD models that are now available within this price point. However my recent experience with the Lypertek Tevis and Sony WF1000XM3’s have made me realise just how good a single dynamic driver can be. I was also somewhat concerned about them using a 10mm driver - having expectations of excessive bass (the Lypertek’s and Sony’s drivers are only 6mm and sound superb). Needless to say, my concerns on both the use of a single dynamic driver and its size turned out to be completely unwarranted.
The FD1’s are made of an acrylic material - with an opaque backplate (black or blue) and a semi-transparent front which shows some of the inner workings of the headphone. The soundtube has a fairly large bore but appears to be pretty much compatible with most tips. The soundtube itself is a metallic gold and features an impressive looking mesh filter at the tip. The supplied tips fit very tightly - I struggled at first but they’re certainly secure once fitted correctly. These headphones appear to be quite thick but don't really look it once they're in your ears. You can comfortably lay on your side whilst wearing them - this is always something that's welcome as I do a lot of my listening in bed.
The cable is really nice - slightly thicker than those found on most other IEM's but they’re really flexible and don't feel sticky. The braiding is tight and it terminates in a really neat right angled gold-plated jackplug. You are left with the impression that the cable is going to go the distance.
One really cool touch was the supplied Fiio branded Pelican-style case - much nicer than the typical pleather pouches normally offered with headphones in this price range. The Fiio’s also come with a range of different tips.
Before going into the sound quality of these headphones - I feel that it's important to go through something of a preamble first.
As a previous owner of the Etymotics ER4P, I was kinda used to somewhat severe insertion depths. Most IEM's don't go as deep as the Ety's and the FD1 is no exception. However, one thing about the Ety's was that it wasn't just about how deep you have to insert them but also ensuring that you equalised the pressure behind them. Failing to do this with the Ety's (and quite a few other IEM's on the market as well), resulted in a thin, somewhat harsh sound character. Once you got the correct degree of 'insertion' the sound really opened up and sounded so much better. The FD1's feature a pressure release valve which pretty much eliminates the need to 'fiddle' around with the earphone in order to get the 'sweet spot'. The only other headphone that I'm aware of that has this feature are the Apple Airpods Pro. With the Fiio FD1 - you just 'plop' them into your ears and that's it - jiggling them around won't make any significant changes to the sound quality (assuming you have a good seal of course).
The Fiio FD1 offer something that I’ve only found on a couple of in ear monitors - rock solid image stability. The Etymotics offered this - clearly Fiio have done a good job matching drivers. Up front, I have to say, these IEM's sound really REALLY nice. My initial concerns about the potential for excessive bass was completely unfounded. Bass goes really deep and yet maintains resolution - textures from lower notes is resolved just as nicely as the other frequencies. I did notice that the FD1’s sounded slightly ‘bright’ on older recordings - but I suspect this is simply a case of the headphones accurately reproducing the recording without adding any artificial ‘bloom’ to the sound.
Another thing I noticed almost immediately was the frequency range from extreme bass to extreme treble was remarkably smooth - no apparent gaps in the frequencies and, for my ears at least, no significant boosting of bass or treble. This is a feature that is always welcome on IEM’s - my Magaosi K3 Pro’s definitely appear to have ‘gaps’ which kinda sound like small satellite speakers paired with a massive subwoofer.
It’s tempting to say that the FD1’s lack the very lowest bass registers but when I tried some of my darker ‘trance’ tracks they deliver bass in spades. The bass is really nice and tight though. They sort of remind me of the fast bass you get on some balanced armature headphones. To sum up - deep, not flabby, detailed and fast.
When I first tried the FD1’s, they were a little ‘shouty’ in the upper mids. This seemed to calm down a little after a couple of hours of listening (although it’s possible my brain did all the burning). The FD1’s certainly can pull details out of my recordings though - I’m genuinely able to hear tiny details (vocallists breathing, additional echos, track layering). They’re perhaps a little ‘strident’ still in the upper mids - this is something I’m normally very sensitive to - but they still sound great to me.
Perhaps slightly reduced compared to the 1More Triple Drivers for example, but they don’t suffer with this. Cymbals perhaps lack some of the metallic ‘sheen’ that can be found with balanced armature drivers, the high details still shine through. I think the best description I can give is that they’re slightly more ‘mellow’ than 1More or Magaosi K3 Pro’s - but this is a sound character I really like.
The Fiio FD1’s are surprisingly dynamic. To me, they share a very similar sound character with the Ultimate Ears Triple Fi 10’s - that’s high praise in my opinion as I rate them very highly. Faster than I expected, sufficiently sensitive to be driven to very high levels with basic players and phones and not so sensitive that you continually hear line noise either.
I'm really impressed with these headphones. They offer a taste of the high-end at a budget price. They're comfortable, sound great and don't require any esoteric hardware to drive them to high levels. Whilst they're not the best for external isolation, they also don't have too much 'thud' when you're walking around with them. Very highly recommended.