Acoustic Research AR-M2 hi-rez portable player February 2017

John Atkinson tested the v.2.5.6 firmware upgrade in February 2017 (Vol.40 No.2):

In April 2016, I reviewed the AR-M2 portable player from Acoustic Research (footnote 1), concluding that "It's good to see the Acoustic Research brand applied to such a well-engineered product after all these years." When I compared the AR-M2 with the Astell&Kern AK240, I found the differences between the two players small, commenting that "on balance, if I didn't have to count pennies, I'd go for the $2500 Astell&Kern—but for $1300 less, the Acoustic Research comes very close." A limited-time, special-offer price reduction from $1199 to $899 last December made the AR-M2 even more of a good buy.

At the time of my review, the Android-based player was running the AR-M2 Music Player app v1.06, which I updated to v.1.2.0 before returning the AR to its manufacturer. Since then, the player's firmware has been updated to v.2.5.6, which allows full hi-rez gapless playback from one file to the next —AR says that many players downsample their look-ahead for gapless—as well as some tweaks to the user interface. I therefore asked Acoustic Research's Rob Follis to ship a second sample to me. This arrived with the older v2.5.2 firmware, so I downloaded and installed v2.5.6 from the Acoustic Research website.

I loaded some gapless albums onto a microSD card and started listening. The first thing that struck me was that I was correct to have recommended this player as highly as I did last April. (That was a relief!) Its sound was smooth yet detailed, with palpable imaging and powerful low frequencies. With a true gapless album such as Pink Floyd's Wish You Were Here (24/88.2k FLAC files, Harvest), all the transitions worked fine. The fadeout of the saxophone solo at the end of "Shine On You Crazy Diamond" smoothly led into the industrial sounds at the start of "Welcome to the Machine," and the crowd noises that end that track blended seamlessly into the flanged guitar riffs that start "Have a Cigar." I thought sometimes that I got a small "pop" when one track was followed by the next, but it didn't seem repeatable.

Acoustic Research had sent the AR-AC71A impedance adapter for ultra-sensitive IEMs ($69.99). This is a nicely made 3.5mm stereo coupler with a series resistance of 100 ohms. Though the plug didn't give a consistent connection with the player in its leather case, it proved useful with my Ultimate Ears 18 Pro IEMs, in that the volume control could be used over a greater portion of its range. However, I felt the sound quality lost some of its spaciousness in the highs and drive in the lows with the IEMs, which have an impedance ranging between 11 and 21 ohms, driven au naturel.

With its v.2.5.6 firmware installed, I continue to be impressed both by the sound of Acoustic Research's AR-M2 and the fact that, when in the vicinity of a friendly WiFi network, it can stream lossless files from Tidal.—John Atkinson

Footnote 1: The AR-M2 costs $1199; the AR-AC71A impedance adapter and the AR-LCM2 Brown Leather Sleeve each cost $69.99.
Acoustic Research
3502 Woodview Trace
Indianapolis, IN 46268
(844) 353-1307

spacehound's picture

I wonder if it can drive a typical 'line' input to reasonable levels? My iPad can't. Nor will its 'Lightning' output at a high enough level into a USB port. You can't really tell from the specs.

So for the future it might be helpful if you could try this and tell us. (I was too tight-fisted to order the optional Burmester audio in my car so now need an external player.)

AR? I've still got, and use, their turntable, later copied by Linn. Bought it from the local branch of Laskys. Do you remember them too?

John Atkinson's picture
spacehound wrote:
I wonder if it can drive a typical 'line' input to reasonable levels? My iPad can't.

It will have no problems driving a line input, especially from the headphone output.

spacehound wrote:
AR? I've still got, and use, their turntable, later copied by Linn.

That's unfair. Yes, both were belt-drive, suspended-subchassis turntables, but that's where the comparison ends. The original AR was still a good turntable but was let down by a poor tonearm.

John Atkinson
Editor, Stereophile

spacehound's picture

Castle Engineering was a small machine shop and copied the Ariston turntable design that they were contracted to make some parts for, right down to the lid, then sold it as their own, changing their name to Linn at the same time. That's how Linn got started in the audio business. There was a court case about it but it never came to anything for or against the two opponents.

Thanks for the AR output data. I tried it and it's fine. But only a demo model, the dealer hasn't got any stock at the moment.

jhanken's picture

In terms of function this is approaching perfect, with PCM, DSD and Tidal, but the omission of MP3 and AAC to me is a bit heartbreaking, I still have some music in those formats that I cannot get otherwise. I am really hoping to have just one portable player for everything. In the review, you said one AAC file actually played fine, any chance you could please test a 320KB MP3 and verify that it would play properly? Thanks, and very grateful for this review!

John Atkinson's picture
jhanken wrote:
In the review, you said one AAC file actually played fine, any chance you could please test a 320KB MP3 and verify that it would play properly?

The AR-M2 player has long since been returned to the manufacturer, but I did play 256kbps MP3s with it without any problems.

John Atkinson
Editor, Stereophile

robfol's picture


The M2 plays almost every format under the sun, including MP3 of all shapes and sizes and AAC, plus FLAC, ALAC, WAV, AIFF, APE DSD64/DSD128 & DXD. Sensible future formats will be addressed by our regular firmware updates.

Unfortunately an error on our website led JA to believe that these base formats might not be supported.

Regards Rob Follis for Acoustic Research

Long-time listener's picture

I spent about an hour listening to the M2 at a local dealer, with my own headphones and music. Aside from generally good clarity and lack of obvious grain or sibilance, its most appealing aspect was its spacious soundstage, which is hard to give up once you've gotten used to it. But at the same time, the soundstage seemed sort of artificially "inflated," and its excellent bass likewise seemed a little boomy or artificially inflated, and the sound was slightly "dry." (And the Alps potentiometer was making noise as it turned.) The guy in the store also told me that downloads of gapless capability aren't available yet for the general consumer, even if they are for John Atkinson--and gapless is a VERY fundamental feature that should be standard on every player.

The Fiio x7 doesn't have that wide open soundstage, but it has a slightly more liquid, full-bodied, and rich character, with equally good clarity and freedom from glare or sibilance. Bass is equally good, and more natural. It also comes gapless out of the box. At about two-thirds the price, I have to consider the Fiio X7 an equally good player and a better value. Combined with the clarity, balance, and full-range response of my single dynamic driver NuForce NE-800M, it sounds marvelous.

robfol's picture


The 2.5.5 firmware with gapless capability and a lot of other tweaks and upgrades will be available within the next 10 days

Regards Rob Follis for Acoustic Research

Long-time listener's picture

And all else being equal, it has to be said that the player with the better soundstage certainly brings the listener one step closer to true realism in sound. And the M2 certainly has the soundstage, so it must be doing something right... If I had known about the M2 sooner, I believe it would be my player now instead of the Fiio.

dce22's picture

Chord Electronics Mojo DAC + Samsung Galaxy S7
4.8 Volt 0.7 Ohm Output Impedance
(Will work perfectly with all the headphones on the market)

Acoustic Research AR-M2
3.7 Volt 10 Ohm Output Impedance
(Will work properly with 100 Ohm or more Headphone Impedance)

Chord Mojo has 10db less distortion and 10 db less noise at all frequencies has better oversampling filter will work with every headphone there is, can be a DAC for your home system and for the same amount of money you can buy top of the line smartphone and Mojo DA instead AR-M2

PS. I am no way affiliated with Chord Electronics or Acoustic Research I am just parroting reality.

robfol's picture

Well, if you are a fan of expensive rubber bands, dangling cables and pocket destroying lumps? then that would be a great solution. In the meantime the M2 is an amazing performer at half the price of relevant competition. Cheers, Robert for Acoustic Research

TheNoose's picture

I wish all reviews would identify if the unit will output balanced audio and to what extent/format. Esp at this level of player. For example the Pono provides this functionality at 1/4 of the price here...and yet this was not tested or used as a benchmark. I wish it was.

robfol's picture


Balanced out adds complexity and cost for in our opinion, little benefit on a portable device. The M2 does not have balanced output.

Regard Robert Follis for Acoustic Research

TheNoose's picture

Acoustic Research is such a renowned brand. I wish there is an opening for me/customers in your statement Robert. It feels like talking to Apple, we know what you need best and aren't listening to you anyway. I wish it wasn't so.
On the ummmm...upside...why don't you buy a couple of balanced out portables say from Astell and Kern and Pono for example and using proper balanced cables and headphones give them a try? I'm sure like me and thousands of other customers and experts you'll hear a difference worth investing in. You could really redefine this facility with the power of your brand...Sincerely.

The Federalist's picture

I was very interested in the AR product when I first stumbled across it on Head-fi, and came very close to dropping $800 on the 2nd gen AK100 but the sheer number of units (from dozens of different manufacturers) up for sale on Head-fi classifieds, on a given day, leads me to believe the product type, while attractive, doesn't have much staying power with people once the whole consumer cycle has been completed and the drugs have worn off.

I would love to see something along these lines that was a larger screen, like an audiophile tablet so to speak, but with the same mechanical transport controls like these smaller units have.

So far the closest I have seen is the Nativ player on Indiegogo but that one is tethered to the wall via mains power so is a different animal.

I do think a lot of people have an aversion to using their phone or their tablet for music delivery. It's pretty clear considering how robust this segment is. I just think a bigger screen would draw you in a bit more. The phone form factor doesn't do it for me.

Either way. A very interesting device and a very good review. I do appreciate your take on this.


The Fed

Boogie6301's picture


Thanks for the review. I'm considering the AR-M2 primarily because of Tidal support. I currently have the QP1R and I'm more than satisfied with its sonic abilities albeit with crappy UI, no streaming and doggy scroll wheel.

Since your review of the AR-M2 came after the QP1R I'm interested to know your comparisons purely from sound qualities. Bluetooth, WiFi and streaming are "nice to have" for me so I'm not willing to compromise sonic qualities with these features.