As part of a tour organized by FiiO, over Head-fi, I was able to spend some time with their brand new DAP, the M25, which is available in two flavours, R2R and AKM delta sigma. The AKM version, called M25 Verita, sports the ΔΣ modulator AK4191EQ coupled with 2x AK4499EX DACs.
The M25 R2R features FiiO’s self-developed 24+5-bit segmented R2R PRO resistor array, delivering rich analog character with selectable Warm and Natural sound modes (source).
The M25 R2R arrives with a laundry list of features and I am thoroughly impressed. For device costing 1249 Eur, it sure packs a lot more features than the competition.
First, let’s look at the physical aspects. The device has an aluminium frame, keeping the weight down to a mere 344g, which is less than Nipo N2 (375g), LP6Ti199 (365g) and a lot less than Astell&Kern SP3000 (543g). All values are measured with the respective cases one, hence a slight difference from the official values is normal. The dimension are reasonable, 140x78x18mm, which sets it just a bit larger than the LP6Ti199 (135x67x23), but also thinner. For reference, the Nipo N2 is 137x74x20mm. In short, one of the most satisfying to hold DAPs of the new generations, in a landscape dominated by monstrous bricks. I applaud this.
Two things catch the attention, the presence of two USB-C ports and the Desktop mode switch. The USB 3.0 port can be used for data and/or charging, while the Power in port is used exclusively for charging, with no data transfer functionality. QC and PD fast charging protocols are supported. Once a fast charger is detected, the M55 offer the possibility of setting the gain to Super High, unlocking the full 1700mW/channel power.
In addition, while connected to power, flipping the desktop mode switch disables the battery charging and lets the DAP run on DC. This is useful if you want to use it as a desktop DAC/source, since you don’t have to worry about battery degradation. No fast charger is required for this function.
The power button is located at the top, surrounded by an LED light that also serves as a format/resolution indicator. Plenty of options are available, deactivate it, sync it with the screen, constantly on, etc. I love the amount of customization possible with this DAP.
On the left side, we have the volume buttons (yeah, sadly M25 uses buttons, not a volume wheel) and a Multifunction button that can be set from the menu. Sadly, the number of options is limited and i couldn’t find any that suited my use case. For example, there is no option to set it to bring up the Audio settings page. The most useful I could find were the Enter USB DAC mode and Change personalized sound.
The DAP has 5 different working modes: Android Mode, Pure Music Mode, Airplay, USB DAC Mode and Bluetooth Receiving Mode. These can be selected from the drop down menu, or assigned to the mUltifunction button. The names are self explanatory, suffice to say the Pure Music Mode is based on the FiiO Music app, which works quite well. No restart is required, the switch is seamless.
One more feature I like is the tap-to-wake. Even though I am greeted with a warning this will reduce battery life, it is a worthy trade-off for me.
The DAP has FiiO Music installed by default and also has a library of apps (FiiO Market) from which one can easily install streaming apps, even without logging into Play Store. Good thinking.
The initial scanning of the card was a lengthy process for me (around 60 min), but afterwards I did not have any hiccups.
In terms of sound-shaping, a small number of options is available, NOS or OS modes, DRE and All to DSD.
M25 is a DAP that plays hard on the interaction with the IEMs. It has interacted very well with some, was indifferent to others and downright underwhelming with one.
With Aful Miracle One – a newly released single DD of only 6mm. This is a small IEM that requires big power. M25 provided that in spades, bringing a fullness to the sound I could not get with the SP3000. With M25, Miracle One had more bass, a deeper stage and fuller sound, while carrying more note weight. In contrast, SP3000 had it sound slightly thinner, but with more detailed treble, at the same time eliminating any rogue peaks. Quite a dynamic presentation, trumping the somehow anemic SP3000.
With Oriolus Traillii – M25 restricts the stage’s width, while maintaining the height and adding a bit of depth. There is a catch here, as the depth is not distributed in a conventional way, in front of me, or front and back and certainly not everywhere, like the LP6Ti. With M25 R2R, I hear the voice in the middle, dead-central, with not much around it, then immediately L and R the parts with the highest depth, and quickly dropping towards the periphery of the stage. N2, in stark contrast, has a lot more width, and the depth is slowly diminishing towards the periphery, but even at the very edge, it retains some depth (some elements are nearer or further on the Z axis. Overall, N2 creates a more spherical stage, which is what I come to expect from Traillii.
Another interesting find is the dynamics. M25 seems to be more focused on textures than shear dynamics, thus requiring a hefty volume increase to obtain the same impact as the punchy N2.
WIth Elysian X – This is an IEM that I like to listen at higher volumes, where it lights up like a supersonic engine. M25 builds up a coherent stage, still maintaining a sort of blind spot in the dead centre, but with more depth throughout. Bass control is exemplary, maintaining the mid bass afloat X’s hefty sub bass. X has an over-expressed upper mids section that here sounds perfect. The effect it has on X is similar to the desktop Teac UD-507. The IEM and DAP work together to present gritty distorted guitars, and vibrating, yet, not grating upper mids.
LP6Ti199 is the king of all DAP when it comes to stage depth. It doesn’t focus on width (and nor do I), but it arranges the elements in a much deeper and taller stage. The end effect is music that sounds more natural and realistic. The instrument separation is at the same time sublime and unassuming, one can easily follow any instrument, but at the same time, there is no clear-cut line, like with other DAPs. Notes across the spectrum have more weight than M25 R2R (and any other DAP I know) and the stage has a lot more depth.
Nipo N2 is another one of my favourites for X. The differences are easily identified: with N2, X sounds a little brighter, more open, outwards going, with more treble energy and definition and with more excited upper mids. While guitar solos are elevated, some female vocals might be borderline shouty.
Fletcher’s live version of girls, girls, girls sounds more boomy, more dynamic on N2 compared to M25 R2R, which in turn is smoother, easier to listen to and with additional note weight here and there.
With Mysticraft Hex – This combo had my scratching my head, as the amazing intricate stage Hex is building with SP3000 is gone. It remains a very good sound, but missing what makes Hex one of my all time favourites. SP3000 has more treble details, better dynamics and much better imaging and instrument separation.
With Storm – M25 R2R (super high gain) drives Storm satisfactorily, with a good reserve of power left. The bass is ample and the control is retained, the spherical stage is largely preserved and the sound is engaging. It does shrink the stage a bit, but adds some height, thus maintaining the grandeur. Bass impact and dynamics are good, maybe not exactly at the same level as the Nipo N2, but fairly close. In simple high gain mode, some of the dynamism is lost, but it remains better than with other IEMs. Of particular mention here is the treble texture. Listening to Daft Punk’s Giorgio, the cymbals sound as if I could touch them, that reach and realistic is the texture. With the exception of the need to play it at a rather high volume, I would say M25 R2R is very close to N2 when it comes to Storm. This is no small feat, considering the N2 was more expensive when it launched.
With Unique Melody Maven 2 – Maven 2 is notorious for its ability to scale up with more power. M25 R2R is happy to deliver and it elevates Maven 2 quite nicely. The stage is mostly preserved, the lower mids get a bit more focus than the mid bass, and the treble more restricted than, say SP3000, which is a good thing and allows for cranking up the volume without any adverse effects.
With SP3000, Maven 2 has a more detailed sound, with a largest stage, much improved imaging and separation and more clarity. Maybe the notes don’t have the same weight, but the feeling of depth and textures are superior.
N2 is authoritative and has nice L/R panning. The bass guitar is more articulated and the microdynamics are better. Turning again to Giorgio by Moroder In the third part of the song, things can get a bit splashy, which did not seem to be the case with the darker M25.
DRE and ALL to DSD
All to DSD adds a bit of air up top and stretches the stage in width. The effects is quite subtle, and in most cases it can be considered an improvement. It takes it in the direction of a more “high res” sound, slightly smoother and more rounded. It’s only a matter of whether you want more grain or more smoothness. All to DSD means that all signal processing before D/A conversion is by passed, so there will be no EQ-ing available. Also, it consumes more battery and generated more heat (which was never an issue with M25 R2R).
DRE has the effect of trading some note weight for brightness. Not really my cup of tea, but it can be useful in some occasions. I also have the feeling DRE does not maintain a perfectly constant volume, with slight ups and downs. If I combine it with the tape graphics, it really reminds me of a walkman, when the tape was misbehaving.
Battery life
I find the 13 hrs official figure a bit optimistic. During my time with it, M25 R2R safely provided anywhere between 9-10h battery life, depending on type of files and the IEMs it was driving, volume, etc. Since emptying the battery completely is not recommended, this is an estimate based on the time it took to bring the battery to 15%. It is possible that the last 10% last more, but a good 10%/1h was consumed throughout the 10 days I had it with me.
Conclusions
As a former owner of the FiiO M33, I can confidently say M25 is an improvement in terms of sound quality, with much improved definition and details, but sounding maybe too flat, in terms of dynamics. There can be many factors to play, gain, volume, settling in (R2R units are notoriously slow to bloom and this being a tour unit, might not have been properly run-in). But, coming from M33 or M21 and looking for a step up in quality, the M25 does just that. Of course, when compared with more expensive, flagship DAPs, some compromises are obvious, but overall M25 performs well within its price range and slightly above. Let’s not forget that Astell&Kern replaced the SR35 with the newly launched PD5, selling for 1059Eur, so pretty close to the M25 R2R, while offering a lot less features and power (I cannot comment on sound quality). I just wish it had a slightly more dynamic sound.
Bottom: Hidizs AP80 ProMax, AK SR35, FiiO JM21