FiiO SnowSky Oak Nano

Snowsky first Flagship IEM is the spiritual successor to the FD7

The Oak Nano was originally planned as the FD17 — the direct successor to FiiO’s FD7, a well-regarded single dynamic driver IEM that used a pure beryllium diaphragm. The FD7 was discontinued when the beryllium supply became unworkable: the material is only manufactured in one facility worldwide, in the United States, and lead times had grown to the point that production could not continue.

The Oak Nano is FiiO’s answer to that problem — a beryllium alloy diaphragm that, according to FiiO, performs closer to pure beryllium than conventional beryllium-plated designs, combined with a titanium alloy shell machined to watch-grade tolerances and a semi-open acoustic design.

At some point in development, the decision was made to release the Oak Nano under the SnowSky sub-brand rather than as the FD17, making it the first flagship IEM in that line at $499. Whether you come to it knowing the FD7 or encountering FiiO’s single-driver flagship for the first time, the Oak Nano is a notable arrival.

I have been using the Oak Nano as my main daily driver IEM for 2 weeks now, fully each day to get a more complete picture of its character than say an evening listening can provide. The first week confirmed some expectations and shifted a few others — in particular, this is a different tuning than the original FD7, while that IEM had a natural slightly V-shaped tuning, but the tuning on the Oak Nano is more inline with some recent FiiO IEMs, I guess more like a modern FiiO ‘House Sound’.

But before I get into the sound, lets have a look at the very nice unboxing experience:

Unboxing and Packaging

The outer packaging is clean and premium — SnowSky presentation without any excess:

You are immediately presented with the impressive looking box with the snowsky branding on it:

Opening the box reveals the earphones seated in a precisely cut foam interior:

The titanium alloy shell catches light well and looks very premium inside this box.

Removing the top you get access to the excellent high-quality cable:

You get a small manual under the box:

Underneath this section of the box you have 2 more ‘drawers’ with extras:

Each layer has lots of accessories:

And there is even a second layer of eartips in one of the drawers:

The eartip selection is genuinely generous — one of the better-stocked tip selections I have seen at this price (or any price):

There were also eartips in the drawer with the cable adapters:

Overall, Snowsky has given you a flagship level of extras with the Oak Nano:

Build Quality and Design

The Oak Nano shell is machined from titanium alloy apparently using watch-grade manufacturing processes:

It is both lighter and more solid than you might expect, so a good quality finish IMO:

The grille design is the most distinctive visual element, and I think it looks very nice:

The cable conductors are also very high quality, and I like how they are color coded:

Nozzle Comparison: Black vs Red

One of the most practical customisation options included in the box is a second set of nozzles:

The default black nozzles present the full Oak Nano tuning — including its treble extension. The red nozzles reduce treble energy slightly for a more relaxed and in my opinion, balanced presentation.

After the first week of use, I actually settled on the alternative ‘red’ nozzles as my daily preference. The extra treble from the black nozzles was not fatiguing, but the red variant brought the tonal balance to what I consider optimal for long sessions. For listeners who prefer a brighter signature, the black nozzles are the obvious choice.

Fit and Comfort

The Oak Nano uses a smaller shell than the trend toward multi-driver designs with large housings that require deep ear insertion or unusual angles. The nozzle angle suits my ears well (as it did with the FiiO FD15), and with the right tip from the extensive selection included, the fit was secure and fatigue-free across full working days.

The titanium shell’s light weight is also a benefit with the lightweight comfort.

Features

The Modular Cable and Adapter System

The Oak Nano’s standout feature is its modular cable and three-adapter system; you get 2 alternative adapters in the accessory box, including a 4.4mm and a usb-c adapter (which has parametric EQ):

The cable itself with the connector screwed into place:

The usb-c adapter is one of the smallest I have seen, here it is compared to the already tiny Truthear KeyX:

USB-C Adapter with Parametric EQ

I always like to see a USB-C adapter included with flagship’s and the fact you get Parametric EQ is the genuinely fantastic, I think. I immediately went and enabled this dongle with my DevicePEQ plugin, so support for directly connecting the Oak Nano into various online measurement databases will appear very soon. For listeners who want to align the Oak Nano’s signature with a measurement target, dial in a custom curve, or simply correct the nozzle-dependent treble behaviour, this adapter makes the whole process straightforward.

Sound Impressions

All listening was done with the Oak Nano connected to a portable DAC-amp source (CrinEar Protocol Max with no EQ) via the 4.4mm balanced adapter, using the red nozzles unless otherwise noted. I also spent significant time with the USB-C adapter directly from both a phone and a laptop to evaluate how the PEQ implementation performs in practice, though these sound impressions are with no EQ adjustments. But I also used the 3.5mm connector with my Macbook Pro without any problems. This is a relatively easy-to-drive IEM.

Bass

Bass extension is solid, with good texture and control through the mid-bass. The low end has genuine weight — this is not a thin, analytical presentation — but it does not overwhelm the midrange that sits above it.

On “Angel” by Massive Attack the sub-bass weight and slow decay are rendered with appropriate authority, and the beryllium alloy diaphragm’s fast transient response keeps the bass textured rather than soft. The semi-open design does not hurt the low-end as much as a fully open back might suggest — the Oak Nano maintains satisfying bass character while gaining the spatial openness of the vented chamber.

Midrange

The midrange is the Oak Nano’s defining characteristic. It is forward — noticeably so — in a way that makes acoustic music, vocals, and instruments with the natural body genuinely engaging.

On “Fast Car” by Tracy Chapman the vocal sits close and immediate, the guitar body is present without being heavy, and the overall sense is of a live performance rather than a recorded one. This tuning is not for everyone: listeners who prefer a flatter, more analytical midrange or a Harman-adjacent response will find the Oak Nano’s presentation too upfront. But for those who like midrange energy — and I am firmly in that camp — the Oak Nano’s character is one of the more enjoyable I have spent time with at this price.

Treble

With the black nozzles, treble is present and extended — there is sparkle and detail, and the beryllium alloy diaphragm’s high-frequency resolution is evident on “Tamacun” by Rodrigo y Gabriela, where the upper-register guitar attack arrives cleanly and with body.

With the red nozzles, the treble pulls back slightly to a more balanced level relative to the midrange, which is where I ended up for daily use. Neither option is harsh, but the black nozzles are the sharper tool and the red nozzles are the more comfortable long-session choice for most ears.

Soundstage

For a single-driver IEM, the Oak Nano’s soundstage is notably wide. The semi-open design is directly responsible: venting the chamber removes some of the closed-in character that limits most sealed IEMs, and the result is a spatial presentation that feels considerably more open than the form factor usually allows.

Imaging is precise, and the mid-forward tuning contributes to a stable, well-defined centre image — vocals and solo instruments are cleanly positioned. Width and instrument separation are both among the strongest I have heard from a single DD IEM at any price, and the effect is one of the things that makes extended listening sessions genuinely enjoyable.

Comparisons

The group comparison below puts the Oak Nano alongside the Crinear Daybreak, FiiO FH19, FD15, and KiwiEars KE4 to show the range of shell sizes and designs in this bracket:

FiiO FD15

The FiiO FD15 uses a magnesium/aluminium alloy shell and a different diaphragm material — the Oak Nano moves up to titanium alloy construction and the beryllium alloy diaphragm, with a correspondingly higher price.

—————————————————————————————	—————————————————————————————–

Sound-wise the Oak Nano is similar tuned with that FiiO midrange ‘House sound’ but to my ear slightly mid-forward and spatially open, while the FD15 is the more conventionally balanced option. At roughly half the Oak Nano’s price, the FD15 remains an excellent single DD IEM; the Oak Nano is the step up for those who want the more engaging midrange character and the semi-open staging.

FiiO FX17

The FiiO FX17 is a hybrid multi-driver design versus the Oak Nano’s single DD approach. The FX17 offers more technical resolution from its driver array and a more analytical presentation. The Oak Nano counters with a more cohesive, natural timbre — a single DD advantage — and the wider semi-open soundstage. These are genuinely different experiences at similar prices, and the choice between them is primarily about whether you prioritise resolution and neutrality or spatial openness and tonal engagement.

Fosi Audio IM4

The Fosi Audio IM4 is a considerably more affordable IEM that punches well above its class. At its price it competes on value rather than outright performance, and the Oak Nano is the clearer driver and the better-built device. The IM4 is the entry to this conversation; the Oak Nano is for someone who has already been through the IM4 class and wants more.

Meze Alba

The Meze Alba is the most natural acoustic comparison point — a single dynamic driver IEM at a similar price with a warm, musical presentation. The Oak Nano is more mid-forward and more spatially open; the Alba is warmer and somewhat more relaxed. Both are enjoyable for extended listening; the choice between them is a matter of preferred tonal character and whether the semi-open staging of the Oak Nano is a priority.

Specifications and Measurements

Full specifications had not been officially released at the time of writing. This section will be updated when confirmed figures are available.

The frequency response graphs tell the most important story. Here is the Oak Nano with both nozzle options plotted against the JM1 target — the mid-forward character is clearly visible, and the treble difference between the black and red nozzles is obvious:

The left and right channel matching on the red nozzle is excellent, confirming the build quality is consistent unit-to-unit:

Compared against the FX17 with both Oak Nano nozzle options — useful for understanding where each sits in the FiiO line relative to the JM1 target:

The Oak Nano against the FD15, you can see they both share a lot of similarities:

A combined view showing the Oak Nano red nozzle and black nozzle alongside the FD15 with red nozzle and foam measurements:

The multi-IEM comparison below shows the Oak Nano alongside the Fosi IM4 and Meze Alba — useful context for how the mid-forward signature compares to the alternatives in its price bracket:

I never reviewed the original FD7, so I haven’t got a compatible measurement, but I believe this measurement was taken with a similar setup to mine, so this might be indicative of the differences, you can see that the original FD7 was a little warmer but wasn’t as forward in the midrange as the Oak Nano:

Distortion figures are clean throughout — the single DD design with the beryllium alloy diaphragm produces minimal harmonic distortion across the audible band:

Rating Explanation

The Oak Nano earns a pragmatic rating of four. It is a genuinely excellent single dynamic driver IEM — the beryllium alloy diaphragm delivers the cohesive timbre and fast transient response that makes single DD designs compelling, the titanium shell is beautifully made, and the semi-open staging sets it apart from most sealed IEMs at any price.

The accessory package — two nozzle sets, three cable adapters including the PEQ-enabled USB-C dongle, and a comprehensive eartip selection — is among the most complete I have encountered from any IEM at this price.

So, the four rather than five reflects that the Oak Nano’s sound signature I feel will be genuinely polarising. Listeners who prefer a flatter, more analytical response or a Harman-adjacent curve will find the midrange presentation too forward, and the semi-open design is a trade-off that slightly narrows the use-case envelope compared to a fully sealed IEM. At $499 the market is demanding, and the Oak Nano asks you to specifically want what it offers.

Features score five without hesitation. The dual nozzle system, modular cable with three adapter types, PEQ-capable USB-C dongle, and extensive eartip library represent one of the most comprehensive accessories packages available at this price. The PEQ adapter in particular is a feature that turns the Oak Nano into a fully tuneable system without additional investment. I am 100% sure we will see a simple PEQ adjustment appear in the next few weeks to give the Oak Nano the FD7’s sound signature (if I had measured the FD7, I would have provided it in this review).

Conclusion

Overall, I feel the Oak Nano is a worthy flagslip for Snowsky, but if you have fond memories of the FD7 and have been looking for a worthy follow-up, the Oak Nano might not be it. But if you want a premium DD IEM with excellent accessories and a vocal forward tuning with a more spacious sound, the Oak Nano is one to look at.

It may not carry the FD7’s name, but the Oak Nano carries something of its legacy, the conviction that a single exceptional DD driver, the right materials and the right acoustic space, still has something to say.