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.
Footnote 1: The AR-M2 costs $1199; the AR-AC71A impedance adapter and the AR-LCM2 Brown Leather Sleeve each cost $69.99.
