Fidue A31s & A63

REVIEW: Fidue A31s & A63 



Driver Unit: 8mm Dynamic
Frequency response: 18 Hz - 20000 Hz
Rated impedance: 19Ω+-10%
Sensitivity: 101+-3db
Distortion: ≤1%
Max Input Power: 20mW
Cable: 1.20m
Sensitivity: -42+-3dB
S/N Ratio: >55dB



Driver Unit: 8mm Dynamic (with Titanium Composites)
Frequency response: 18 Hz - 21000 Hz
Rated impedance: 16Ω
Sensitivity: 101db
Distortion: ≤1%
Rated Power: 20mW
Plug: 3.5mm mini stereo gold-plated plug
Cable: 1.20m


$30 for the A31s
$60 for the A63

Products page: Fidue

Packaging & Accessories:

These two Fidue models differ from each other in almost every aspect, even in the packaging and acc. set. The A31s comes in a regular carton box matching the more common and budget model. The A63 one comes inside a much more fancy, elegant and sturdy box with a more mid-tier 'air' on it.
As for the accessories, the A31s includes 3 pairs (S/M/L) of single eartips and 1 pair of bi-blange, a plastic case and a pair of earguides. Although the A31s is really tiny small it doesn't mean the tips should have been that small as well, even the L size is too small compared to other medium tips. The bi-flanges, on the other hand, are really good, very similar to those included in the Future Sonics universal models and provide a better fit and isolation. The A63 includes 3 pairs of single tips (S/M/L) and 2 pairs of bi-flange (in 2 sizes) and a soft carrying pouch.

Build & Design:

Again, both models are quite different here as well, not just in design but also in materials. The A31s is probably the smallest tiny thing in earphones ever. It's no joke, the translucent plastic housings are extremely tiny, just to cover the 8mm drivers and nothing else, and it's possible to see the dynamic drivers inside. The cable is twisted from the inside with a plastic cover; a bit thin, lacks a chin slider and a proper relief on both ends. The single-button mic. control is placed on the right side. There are no R or L markings or colors, so the only way to tell them apart is by listening (that's how I knew the mic. side).
As for the A63, aside from sharing the identical same cable, it's completely different from the A31s. The housings are made of aluminum in a shiny blue and silver scheme in a more straight design. Both the Y-split and plug are well made of sturdy aluminum too and the cable is well relieved on both ends. The R and L markings are printed on the bottom side of the housings and a dot on the right side strain relief.
Microphonics are about average on both models (same cable).

Fit, Comfort, Isolation:

While both A31s and A63 have a very easy fit, the A31s wins by the furthest margin in comfort and isolation, not only over the higher A63 but against too many, if not all, other IEMs. With the smallest and low-profile design it's not even noticed. The shells look fully sealed and present no driver flex and isolation is pretty good with the right tips.
The A63 is quite different. Even though the aluminum housings weight nothing, the sharper rear part limits the comfort for the long use. Isolation as well is about average, good for daily commute but not suited for noisy environments.


If up to now both Fidue models were too different, then they couldn't be more polarized different beasts in sound signature.

A31s: 'Fun on budget'

The A31s features a not uncommon but nicely achieved U-shaped sound, as meant for the larger customer masses. It shows a very good balance between lows and highs with a darker touch and extra strength towards the bass regions without classifying into the heavy bass category. Mid-bass is strong but not overwhelming, simply a decent mix of quantity, fun and control, with normal speed level and precision for the price.

Mids are a bit recessed, but not more than expected, and show a slight bass bleed from the stronger low-end. Even so, they don't sound really distant, with good body and a warm and rich character; maybe just a tad dry. Vocals are fairly sweet and full and well prioritized for a U-shaped signature.

Extension is somehow limited on both ends and while there's a good depth, the stage feels more closed. The highs do manage to keep the balance and throw some sparkle, and surprisingly, they are well behaved and smooth; no sibilance or harshness noticed at all even on brighter tracks.

Next to the Xiaomi Piston 2, the A31s lacks in extension, control and overall micro detail and air. It also sounds more closed than the very wide stage Piston, but the later have a much colder tonality and is more distant in the vocals dept. and midrange as a whole. The A31s also sounds less boomy than the Piston 2 and RHA MA350, and smoother on the treble end, especially compared to the more grainy MA350 as the A31s show just a little amount of grain on the upper vocals.

In a short comparison against the popular Philips SHE3580/90, the Fidue A31s are better on pretty much every aspect; better control, smoother treble and forward midrange, and could already be considered a fair upgrade.

A63: 'Beautiful sound'

The model is a whole another story. The A63 features a very mid-centered sound. The midrange is simply beautiful, smooth and very open. Very airy, well detailed and layered, evenly weighted from low mids to upper ones. It's very clean and free from lows attack or highs shrill, yet very fun and engaging, showing a really good instrument separation. Vocals are well separated and layered and simply shine on the A63; it's definitely a vocal highlighting phone which is not commonly found in this price bracket (with the exception of the Ostry KC06/06A and Vsonic VSD1S). The A63 may not match the RE-400 vocal presentation or even the similar priced KC06 and KC06A, but already sounds better than the VSD1S in balance (although the Vsonic still has that 'special' upper vocals feature).

While the bass is soft in impact and rolls a bit early, it's tight and very controlled. Much softer than above VSD1S and less extended than even the KC06. Treble is well present, mainly at the lower treble region to give better body and energy to female singers and instruments, and enough to remain smooth with zero sibilance and distortion even at higher volumes.
Soundstage is not large but the necessary for a mid-focused set. Still, the A63 are well resolving and fairly spacious.


All-in-all, Fidue is offering two nice contenders on their first steps into the fast growing in-ear monitors' world. While the A31s may not be revolutionary in its SQ alone, the special microscopic design is worth taking note. On the other hand, the A63 might lose in comfort matters next to other competitors, but sound wise is simply beautiful.