Xiaomi Piston Air (Xiaomi Capsule): Chill Pill

Chinese electronics manufacturer Xiaomi has, since their inception, a proven track record of providing well-specced gadgets at very competitive prices. Though their earphone lineup is easily outclassed by many other brands both within and outside China, they still have a sizeable following, and I am one of those followers. In fact, their second-generation Piston earphones were one of the first earphones I reviewed over the course of this so far four-year journey. Hence why we will be looking at one of their latest offerings, the Xiaomi Piston Air. Designed not as a successor to the main Piston earphone lineup (we have the Hybrid and Hybrid Pro for that), the Piston Air — also known as the Piston Capsule — is a non-isolating earphone marketed as being free and lightweight, focused on relaxing, all-day comfort. It is an interesting concept, no doubt, but how well has it been executed? Find out after the jump.

TL;DR: An otherwise decent performer at under $15, its overall design limits its usability to one of those earphones you can only use at home – and it’s not really that good there, either.

== Aesthetics ==

Packaging, Accessories

The Piston Air really doesn't come in much beyond a minimalistic cardboard box. No accessories, no carrying pouch, nothing. If you were expecting such accessories then I'm sure you would be no doubt disappointed — especially when you consider that previous Xiaomi earphones were pretty well-equipped. Though a carrying pouch or case may have been nice, the lack of it does sort of drive home the whole "wear all day" marketing pitch. That is, if the Piston Air is as comfortable as advertised, they would spend much more time in your ears than in a pouch or case.

Design, Build, Microphonics

The Piston Air, true to its name, has one of the lightest and most minimal builds I have seen in a while, so much so that they look and feel unusually flimsy for a Xiaomi earphone. However, flimsy does not seem to be in Xiaomi's vocabulary as the Piston Air stands up to a little rough-housing pretty well. Of course, the build quality is not what we're here for — the star of the show is most definitely the Piston Air's unique housing design.

Their metal housings are almost completely draped in an outer "skin" of silicone, which makes sure your ears experience no discomfort or scratching. These metal housings utilise what Xiaomi calls a "spiral damping system" which supposedly improves bass output despite its open-air fit. We'll find out later to see if these actually work or not.

Fit, Comfort, Isolation

One of the key marketing points of the Piston Air is their comfort, and boy do they deliver on that front. The minimal build keeps the entire assembly incredibly lightweight, and their soft silicone housings sit just outside the ear canal for an unobtrusive, barely-there fit. Of course, their half-in-ear design means noise isolation takes a large hit, but this works in tandem with the Piston Air's other key design choices to create what are one of the most comfortable earphones I have ever worn. However, it is also worth noting that Xiaomi is unusually particular with how the Piston Air is to be worn — that is, it must be worn like an earbud as their sound changes quite drastically depending on how you wear it.

== Sound ==

Specs

Headphone Type	Closed-back, half-in-ear monitor
Driver Type	Single 7mm dynamic
Frequency Response	20 – 20,000 Hz
Max. Input Power	N/A
Sensitivity	93 dB
Impedance	32 Ω
Weight	Unknown
Cable	1.25m (~4 ft.) OFC cable
Connector	3.5mm (1/8 in.) straight TRRS connector
Accessories	N/A

Equipment, Burn-in

The source devices used for this review are a fifth-generation iPod Touch and an iPad Air 2. The test tracks I use for my assessments are of various genres ranging from classical to electronica, with the audio file formats varying from 256 Kbps AAC to 24-bit FLAC. Some of these test tracks will be linked to in the sound assessments to demonstrate certain points.

Prior to the assessment I listened to the Piston Air for at least 40 hours to get more accustomed to the sound – otherwise known as "brain burn-in" – to dispel any "changes" to the sound after a certain amount of time. No changes were noted over the review period.

Sound Quality

Bass:

Being a half-in-ear earphone, I don't expect a very moving bass performance from the Piston Air; this assumption has proved to be correct as the Piston Air's bass can be described as lean at best and non-existent at worst. Their lack of a seal in the ear canal allows most if not all of the frequencies below 300 Hertz to simply dissipate into the air, leaving only higher-frequency overtones to reach your ears. This makes a majority of high-intensity music such as EDM and metal outright unlistenable on the Piston Air (M2U — Magnolia; Slipknot — Psychosocial), despite how other "half-in-ear" earphones such as the DUNU Titan and the Superlux HD381 series have much more well-rounded bass response.

Midrange:

The midrange, meanwhile, is a different story. Vocals are placed up front-and-centre and are represented with a slight bit of warmth to give lower registers a bit of heft (offonoff — gold; ProleteR — U Can Get It; WRLD — Hideaway), and a slight hint of top-end sparkle to add sheen to the upper octaves (M2U — Yoake no Uta; Heize — Underwater). It isn't the kind of midrange that goes up in your face; it's laid-back, relaxing, and really lets you vibe out to certain kinds of music. Its open-air design does make the midrange quite prone to resonant peaks which is unwanted in most cases, but in my opinion I feel like it gives the Piston Air a sort of light, fluffy feeling that fulfills the earphones' namesake.

Treble:

The treble of the Xiaomi Piston Air is, on its own, quite mediocre. It's quite mellow, doesn't extend very well, and is far from detailed. However, it does fit quite well in the Piston Air in the grand scheme of things. Its laid-back quality makes for a relaxing, fatigue-free listening experience, and this shows through regardless of what you listen to.

Soundstage/Presentation:
The Piston Air has a pretty decent soundstage owing to its physical design. However, one must not wrongly assume that the Piston Air's sound feels a lot larger than it is — that may or may not actually be the resonant qualities of the midrange. Unlike other "half-in-ear" earphones the Piston Air lacks the quality to let you perceive any noticeable "height" in a recording, which in my opinion does detract from the experience quite a bit.

Genre Proficiency:

The lax, laid-back qualities of the Piston Air allows it to work quite well with slow music with strong "chill-out" moods. As of this writing, I find them to work exceptionally well with vapourwave (HOME — Resonance) and chill hip-hop (ProleteR — Miss Her). With this in mind, I expect they will also do quite well with ambient and some acoustic genres, and maybe a bit of psychedelic rock. However, their mid-centric sound signature will not be able to keep up with the dynamics of more energetic music, and as such I cannot recommend them to anyone who primarily listens to those.

Other Media

I'm going to put it simply — unless you watch only meditation or yoga videos and play Dots, Solitaire, or any other game that has a sort of zen-like feel, the Piston Air will fail to satisfy.

EQ Response

The Piston Air is one of the rather rare earphones I have reviewed so far that does not respond particularly well to equalisation. In retrospect, this is no surprise — after all, much of its sound signature is shaped by acoustics (in other words, how it sits on your ear) and not driver tuning.

Value

The Xiaomi Piston Air retails for 69 Chinese Yuan (about $11) in mainland China, but they usually sell for slightly more than that overseas. One of the cheapest sources for these earphones is Gearbest.com, which sells them for about $12. It's a cheap earphone, sure, but it's not exactly what I'd call the bargain of the century.

== Conclusion ==

The Xiaomi Piston Air has a lot of the good bits that make up a great budget earphone: a light build, decent durability, and a comfortable fit. However, it class short because of one thing in particular — its lack of versatility. Its sound signature is something that works with only a narrow band of genres from the wide spectrum of musical styles that exist in the world. Its physical design is also not something that would work in all situations at all times. For instance, its build, while not terribly bad, is not something you'd take out on a morning run. Its lack of isolation means you will have a hard time enjoying this on the commute.

All in all, it's not a dreadful earphone by any means, but if you don't have much else to spend on a nice pair of earphones, you would want to avoid these.

Category	Score
Packaging, Accessories	3/10
Design, Build, Microphonics	6/10
Fit, Comfort, Isolation	4/10
Bass	4/10
Midrange	7/10
Treble	4/10
Presentation	5/10
Other Media	6/10
EQ Response	5/10
Value	6/10
Total	5/10