Astell&Kern AK100 w/ Martin Logan Mikros 90 review


Awareness. Did you know Martin Logan made headphones? Until receiving this review pair for baselining the (forthcoming) KEF M500 review, I didn’t. The Mikros 90 are ML’s on-ear, noise isolating model (AU$399). There’s also the Mikros 70 in-ear ‘phones.

In Brisbane there’s a hifi retailer who (pro)claims that he sells “Gentlemen’s amplifiers”. Hmmmm. It’s snobbery writ large but his phrasing tells you a great deal about the retailer’s target market. I suspect Martin Logan is pitching to a similar demographic with their Mikros 70/90: 40+ males whose luxury spending is more footloose and fancy-free than young’uns. Read the Mikros 90’s promotional blurb: their ‘executive styling’ is evident throughout. From the faux-leather-styled box to the lightweight aluminium tubing and its leatherette covering, the Mikros 90 ‘ are less Beats Generation, more Beat Generation.


The iOS-compliant, in-line transport controls don’t respond with the affirmative click that you find in Apple’s supplied white-wired buds. A firmer push is required but everything all functions as described: volume up, volume down, pause/play, track forward, track back. Not just a feature for power-suits, an embedded microphone handles phone calls. Unlike KEF, Martin Logan don’t supply a second cable without the inline controls/mic – I’d ask them to reconsider given the expansive Android market as well as the smaller niche of Astell&Kern owners. You could BYO but you’ll need slimline terminations – the left-cup socket is countersunk.

Build quality and comfort. Aluminum over-the-head tubing sees the Mikros 90 clamp tight to the head. This might be too tight for some? The upside is they don’t threaten to fall off during vigorous treadmill listening sessions or when hunched over a keyboard – they stay put. The Martin Logans are more suited to sound-tracking exercise than the KEF M500 which don’t fit nearly as firmly and are 35g heavier than the Mikros 90’s 163g.

Taking time to find the optimal on-ear position is essential. Small peturbations solicit proportionally larger aural changes (than other headphones). Sit them closer to the face and there’s a tendency for the leatherette-covered cups to flip inwards. Turning tale on this minor frustration could bring good news for those with bigger, protruding ears. Once sorted, noise isolation snaps into effect and soundstaging (such as it is inside one’s head) also snaps into focus. A process similar to positioning loudspeakers.


Sound. Midrange clarity is stellar. The Mikros 90 mines low bass notes just fine but the presentation isn’t what you’d call weighty or heavy – these on-ears recall the Sennheiser HD238 talents with speed and bounce. Did I mention that the midrange is superb? If these Martin Logan ‘phones were speakers they’d be likened to LS3/5a monitors. There’s brilliance in the presence region (upper mids, lower treble) that’s counterbalanced by an overall reticence with more bombastic music choices. Capturing all the euphoria but none of the impact of Pet Shop Boys’ “Vocal”, these are not headphones for technicolour pop or crotch-grab rock n roll. Their strengths lay above the waist: strings, acoustic guitars, Female vocals, delicacy, tenderness, timbre, tone. Perfect headphones for the Diana Krall and/or Joanna Newsom fan. As our friend in Brisbane might say: Gentlemen’s headphones.

A bigger problem with greater transparency is the reveal portable source flaws. With either KEF M500 or Martin Logan Mikros 90 in tow, I could easily pick the iPhone 4’s shortcomings with musical layer separation, treble extension, expansion, in-out pressure, tonal colour depth. This portable device just can’t compete with a CEntrance DACport-charged MacBook and it’s miles from the Burson HA-160 sound. The iPhone + AKG K-702? I can’t get no satisfaction.

Hi-res wings also get clipped. iOS app FLACPlayer might claim hi-res (96kHz, 192kHz etc) playback smarts but the onboard decoding chip sells it short: everything is down sampled to 48kHz. The iPad does native 24/96. iPod Classic? 16/48.

From Ken Rockwell’s website: “Wasting time with ‘Audiophile’ DACs and other fluff usually degrades the sound more than just using the self-powered iPhone 5 directly as a source.” That made me chuckle. He’s obviously never heard CEntrance’s Hi-Fi M8. But what if sidecar-ing your iPhone isn’t what you’re after. What if you just want a new bike?

Enter the Astell&Kern AK100. The sub-brand name applied to iRiver’s range of luxury portable media players might connote London law firm but the design is straight outta South Korea.


To circumvent unnecessary waffle the AK100’s key ingredients are as follows: 5.9cm x 7.9cm x 1.5cm (125 g), brushed aluminium casework, 2.4″ QVGA (320 x 240 pixels) IPS touch screen, Wolfson WM8740 DAC, optical input/output, 32Gb onboard memory (expandable to 96Gb with 2 x 32Gb micro-SD cards), comprehensive file format compatibility (FLAC, APE, WMA, OGG, MP3, AIFF), PCM decoding up to 24bit/192kHz, ~15 hours playback time, on-the-fly user EQ adjustment.

Recent firmware updates have added TWO additional key features whose absence had (until now) kept me away: Apple Lossless (ALAC) decoding and gapless playback. I’ll say it again: gapless playback is not some audiophile nicety. It should be standard in any and every software or hardware digital audio engine.


Fire up the AK100 itself and you’ll see MQS. It stands for Mastering Quality Sound – iRiver vernacular for anything that’s 24 bit. Load a selection of such  material onto your AK100 and each song will be listed under the MQS menu option.

Aside from spruiking the hi-res agenda, I’d question MQS’s practical application here. If you drop a LOT of 24 bit material onto the AK100 – which I suspect many users will do – the list soon becomes long and awkward to navigate. Browsing the folder structure or by ‘albums’ and ‘artists’ categories (indexed via library tag scans) was far more efficient for this user.


To borrow an Apple word, the A&K user interface isn’t as ‘snappy’ as those coming out of Cupertino. Then again, the AK100 isn’t terrible. The usual finger pointing works transport and volume attenuation but I found the hardware playback controls more satisfying; for which there’s no need to engage the screen. More juice from the battery! Mind you, that protruding volume pot is cruisin’ for a bruisin’.

Fumble!  Headphone socket output impedance is the AK100’s Achilles heel. The spec sheet rings it in at 20 ohms – whoops. John Atkinson recently measured it at 22.5 ohms – whoops again. Even the iPhone 5 comes in at 4.5 ohms. Finding the right headphone match might be more of a dance than you’d bargained for. Might.

Too high headphone impedance and you won’t get the drive or volume levels you’re looking for. Too low and you’ll hear frequency response anomalies – too little bass, pronounced upper-mids, rolled off treble. Be careful not to overdraw on assumptions based upon nominal impedance ratings. As with loudspeakers, impedance swings throughout the frequency range will determine your fate. Predictably, nothing beats real-life listening.

I imagine this is how iRiver arrived at their own shortlist of recommended headphones for the AK100:

  • Denon AH-D7100 (25 ohms)
  • Audio Technica ATH-W3000ANV (40 ohms)
  • Beyerdynamic DT1350 (80 ohms)
  • Shure SRH840 (44 ohms)
  • Shure SE425 IEM (22 ohms)

Back down under and down home, the KEF M500 step in at 32 ohms, the Martin Logan Mikros 90 at 26 ohms. Both are reasonably well driven by the AK100 – I certainly brooked no quarrel with either’s presentation but most of my listening took place between 60 and 70 on the volume dial (which tops out at 75). In an attempt to dial down the prominent crunch and crack of the Mikros’ upper mids, I delved into the advanced options of the AK100 for user EQ. Enabling it softened the sound, even before making any frequency specific adjustments. A happy accident.


A pair of Kind C-Ear X CIEMs (160 ohms) fared less well: treble rolled off too early and dynamics were sent to bed with no dinner. These Germans sound better with the iPhone 4! (A happier ending for the C-Ear X will be told in my coverage of the AK120).  For those that don’t wanna do the can-can, iRiver recently collaborated with Japan’s Final Audio Design to bring Astell&Kern-branded IEMs to market: the AKR01 – 16 ohm impedance, US$199 (not tested here).

If you’ve already found a pair of must-have ‘phones then hit up Vinnie Rossi at Red Wine Audio for some seriously good mods, one of which corrects the ~20 ohm output impedance.

Did you know that the AK100 can serve as a portable DAC/head-amp? There’s an optical input socket for lassoing one’s laptop. July 2013’s firmware update brought similar input magic to the USB socket. Upon connection to the host PC’s USB port, the AK100 asks you if you wish to charge, mount the storage for adding files or run it as a USB DAC. It’s always nice to have choices. (More on this to come in due course).

Reviewers have a responsibility to their readers not to run away with themselves, to gird themselves against praise that is overly-rooted more in emotion. Such sweet talk rots teeth. A self-centred rave is a poor substitute for genuine insight: ‘X sounds better than Y’ is far preferable to ‘I love this, man’.

With that a priori qualification out of the way, I feel compelled to tell you why I dig the Astell&Kern sound all the way to Mars and back. And yes, the AK100 trounces the iPhone and Samsung Galaxy S3 on sound quality. The deltas are LARGE…

Soon after turning 23 I made my first move from share house to solo apartment. I was becoming a grown-up. I recall the feeling of maturity as my belongings now moved from one large-ish bedroom to occupy several separate spaces: bedroom, bathroom, lounge and kitchen. Everything that I then owned had room to breathe again – it wasn’t packed in – and my life had space with which to continue growing without congestion.


Switching up from iPhone 4 to Astell&Kern AK100 mirrors that memory. Music has more space in which to work; the AK100 has none of the music-as-mulch presentation that plagues the iDevice. The South Korean massages tender pointillism into detail excavation, throwing open the windows on the room and affording the band playing inside one’s headspace more light and more air. The AK100’s virtues are more prominent up top than down below.

The bite down from Apple to Kern(el) took little more than fifty minutes. Fifty minutes that started with, “I’ll just listen to the opening song on Tom Waits’ Raindogs through the Mikros 90 and then that’ll be lunch.”. As “Singapore” shuffled into “Clap Hands”, I had to sit down. By the time side one closer “Time” closed (ha!) I was stretched out on the couch didn’t surface again until “Anywhere I Lay My Head” had growled to a halt.

The listening sessions that ensued saw me reach for approving verbiage again and again and again. I suspect many A&K introductions will tumble down to the same conclusion: what is heard cannot be unheard. Adam cannot uneat the Apple. Eden = delight. The Astell&Kern AK100 is the single greatest leap forwards in private audio since the advent of the iPod. Thing is, the AK120 is even better. Stay tuned for more.

One final thought:  With imported hifi gear often costing more in Australia than overseas, it’s refreshing to see the local Astell&Kern distributor selling the AK100 below USA price parity (AU$649 vs US$699).  This compliment folds double when set against the broader economic backdrop of our weakening local currency (against the US dollar).


Further information:

Astell&Kern | Addicted To Audio
Martin Logan | Advance Audio Australia


UPDATE September 2013: Martin Logan have discontinued the Mikros 90 headphones.

Written by John H. Darko

John lives in the NOW + HERE = NOWHERE. He derives an income from the ad revenues of DAR. John is also an occasional staff writer for Stereophile, 6moons and TONEAudio.

Twitter: DarkoAudio
Instagram: DarkoAudio
Facebook: DAR


Leave a Reply
  1. Please, do not concern yourself with what Mr. Ken Rockwell says. He uses similar proclamations in the world of photography. Just ignore and move on… 😉

  2. John
    Great review as always, I sense much enthusiasm for this player in the piece. One thing I imagine most would consider before buying the AK100 is… should I stick with iDevice/equivalent and pimp it with, say, the CEntrance HiFi M8 instead? OK one won’t get hi-res music but I wonder if many consider that a luxury one doesn’t need on a portable device.
    Did you per chance do a compare the AK100 with an iDevice and added amp/dac?

    • KEFs are more of an all-rounder. These are better suited to lighter, more midrange-centric music.

  3. Great & very good post. Thank you.

    Please review the AK120 and a comparison with the AK100.

    Thank you.

  4. I’m also the proud new owner of an AK100 myself. For me, I felt like I somehow manifest this device into existence. I was pondering an easy way to play 24bit flac files on my system without the fuss of a pc connection. Something with a toslink output that I could feed straight to my amp. I wonder if such a “magical” thing even exists? Well Google was all to happy to inform me that it did. Enter the AK100. Even better I could acquire one right here in OZ delivered straight to my door.

    Many would scoff at the price, but for some reason it wasn’t an issue for me. I’ve been an idevice owner since day one but I was ready to move on. In an age where music convenience has evolved from MP3s to streaming services, its refreshing to see a return to high quality listening in a digital form. This little player is the best of both worlds, able to play studio quality FLAC, small enough to fit in your pocket.

    Great review, its good to hear others gushing over this great little piece of gear.

  5. One regularly hears people complain about the state of manufacturing in Australia. Meanwhile, financial markets, always looking for a means for speculation, jump on any news of allegedly improving numbers not least volumes of goods manufactured. Apparently markets exist for all these bits and pieces.

    What I don’t hear is mention of the quality of manufacturing whether in Oz or offshore. My experience suggests that manufacturing is in a qualitative slump. That is to ask, how many manufacturers inspect the goods they produce? Experience with products from HiFiMan, Silvercore, iRiver and LaCie suggest very few. The Silvercore product did the primary job as stated; pity about the enormous noise taking the place of hum. The HiFiMan Zeros broke. The LaCie external hard disk (P’9230) may be on, it may not; the light certainly isn’t. So much for ‘total reliability’. And iRiver AK120. Where to begin?

    The Astell & Kern AK120 (designed by iriver Ltd. based in Seoul, South Korea and manufactured, according to the firm’s website, at a location about Songshan Lake, Dongguan, Guangdong, China) is ‘the ultimate portable high-fidelity audio system’. On the evidence iriver Ltd. does not hold with such prosaic matters as product inspection after manufacture. For a time, in the instance of the unit that I purchased, the only function seemed to be that of DAC. About a week later it became possible to add music files and hear them. The AK120 has three ‘hardware control buttons’, two work, one does not. Power saving facilities work only intermittently. Likewise, the much-lauded volume control is thoroughly untrustworthy; it might work, it might not, mostly not. Given that the volume control is unreliable, it is no longer of use as a DAC (the difference in levels between use as DAC for which I use very different headphones, and overnight listening is too great to risk the latter). Firmware updates simply do not open. So much, in my view, for computer audio and contemporary manufacturing generally.

    • Sorry to hear about your woes. Did you return your faulty AK120 to the retailer for a warranty claim?

  6. Hi, Paul,

    I am not the owner of the AK-120 and I probably never will be one, but it sounds to me as if you are one of those persons who never read instructions. You could be surprised how much more you can get out of your tech devices if you actually read instructions, and if that is not enough – go through as many on-line reviews and fora as you can find. More often than not, you can get solutions for your problems that other people encountered before you. The collective experience and wisdom is really worth exploring and taking advantage of…