After a year and a half of regular use, Fiio's M23 audio player is still going strong. What I enjoy the most about the M23 is the power and neutral sound — it basically allows IEMs and connected headsets to shine, and it lets me access to my favorite music platforms, including Roon.
Coming in at $719, the M23 is solidly in the mid-range, so when Fiio said it was rolling out a new model that's much more affordable, I was interested. The M21 has a smaller 4.7-inch panel and 4,000mAh battery, but it lasts longer, and it comes with Android 13, which in itself is a big deal as most other audio players I'm using are still on Android 10 or Android 12.
What's notable is that the M21 costs $329 on Amazon, making it that much easier to recommend. Oh, and did I mention it has 950mW of power at 32Ω? That's unheard of in this category. Finally, Fiio has a delightful cassette case aimed at the M21; the case makes the audio player look like a cassette player — much like the Fiio CP13 — and this is easily one of my favorite Fiio accessories.
With that out of the way, let's get to the design. The M21 has a distinctly different feel to it than other Fiio players, and I like the new aesthetic quite a bit. The rear of the device has a frosted glass finish, and it makes holding and using it that much more comfortable. If anything, it feels closer to a phone-like finish, and I like it a lot.
Another positive is that the finish prevents smudges and micro-scratches, and this is a big deal — my M23 constantly needs cleaning, and I just didn't have to bother doing that with the M21. The smaller size also makes a difference in usability, and at 193g, the M21 isn't anywhere as heavy as the M23 or even the M15S. That's a good thing considering it is made out of aluminum, and the build quality is just as great as Fiio's high-end players.
The 4.7-inch 720p resolution is decent enough, and while it doesn't come close to what you get on most phones these days, it is entirely serviceable. The audio player gets the power button and volume rocker on the left alongside the multifunction button, and they have good tactility. The playback controls are on the right, and again, they have good feedback.
I like that the buttons are accented in gold; this differentiates the design a little bit, providing a nice contrast to the blue hue of the device itself. The M21 gets a single-ended 3.5mm port alongside a balance 4.4mm out, and you get USB-C connectivity in addition to a dedicated USB-C port that solely draws power. This is useful because the M21 has a desktop mode, allowing you to bypass its internal battery and solely use USB power.
This ensures the battery isn't affected when using the M21 in desktop mode, and I'm glad to see this mode available on what is ostensibly a budget player. Rounding out the connectivity, you get a MicroSD slot. The M21 also gets pogo connectors on the rear, and these are used to pair it with the unique cassette case.
The cassette case is much better than the usual leather cases that Fiio has with its digital audio players. I get why it isn't bundled, but if you're interested in the M21 and are hankering for a bit of nostalgia, I highly recommend getting the cassette case. It not only provides much-needed protection, but you also get physical controls — you can change music playback controls and adjust volume, with the case connecting to the M21 via magnetic pogo connectors.
In fact, in this mode, the M21 solely relies on physical controls, and it turns the device into a cassette player, and it's just plain cool. I'll admit that I used this mode a lot more than I initially imagined, and the novelty doesn't really go away. The case itself is made out of plastic, but build quality is decent, and I haven't had any issues with it. The only quibble is that when you slot the M21 in the case, you lose access to the buttons on the left side of the device.
Switching over to the software, the M21 comes with Android 13 out of the box, and you get full access to the Play Store. Fiio has its own app market that lets you install all mainstream music platforms, and like the M23, the M21 ties in nicely with Roon. You also get Tidal, Spotify, Qobuz, Apple Music, Amazon Music, and just about any other music service you need.
The M21 is powered by the Snapdragon 680, and it gets 4GB of RAM and 64GB of built-in storage. On the music side of things, it has a quartet of Cirrus Logic CS43198 DAC chips, and a custom TI OPA1692 alongside SG Micro SGM8262-2 amps. It also includes a Bluetooth 5.0 modem with the entire AptX suite.
The UI is plain Android, and the interface is a little faster than even the M23. You can easily slot in a 2TB MicroSD card and then use Fiio Music if you want to listen to music locally. There's a 4,000mAh battery, and the M21 lasts over 11 hours between charges. This is better than what I usually get with the M23, so again, the affordable model wins out.
Coming to power, the M21 provides 380mW at 16Ω and 290mW at 32Ω over the 3.5mm port, and 540mW at 16Ω and a generous 950mW at 32Ω via the balanced 4.4mm connector. Obviously, that kind of power is overkill, and in my use, the M21 managed to drive just about every IEM and headset I connected to it without any issues whatsoever. I used it with the Fiio FT7 and FT5, switching over to the Thieaudio Monarch MKIII IEMs occasionally.
The sound signature is similar to other Fiio digital audio players, with the M21 offering a neutral sound with a hint of warmth that livens things up. There's good energy in the low-end, clean mids with a focus on vocals, and good treble without any sibilance. It isn't as resolving as the M23, but it is mighty close, and it is much easier to use, and I ended up just switching to the M21 because of its portability.
Ultimately, the M21 has proven to be a realization. It has several tangible benefits over Fiio's costlier models, and it delivers a clean sound and plenty of power to drive demanding headsets. The design is much better as well, and on the whole, I think this is a better choice than just about any other player in this category — it's that good.
The M21 has a better design than the costlier M23, and it runs Android 13. The smaller size is better in daily use, and it has Fiio's signature sound, and power to drive the most demanding of headsets.
