[Updated on 08/21/13: Rick has provided a pair of MA850G/B for comparison. A brief comparison is presented here along with the result of his personal request.]
In September of 2012, along with the release of iPhone 5, Apple introduced their innovative earbud, Earpods. In addition, they revised their classic dual-balanced armature IEM, MA850G/B, to ME186LL/A. Other than the remote configuration, nothing is known about the detail of the revision.
First released in September 2008, Apple In-Ear Headphones was one of the earliest dual-balanced armature IEMs that were actually marketed for affordability, whereas its dual-driver competitors, such as Shure SE420&SCL4, Ultimate Ears Super.Fi 5 Pro, and Westone UM2 were considered high-end. Highly praised for its value by many Apple product users, nothing was really known about its electroacoustic property, other than the official frequency response graph shown above. Enigmatically, Apple not only set the y-scale unusually high, the x-scale was also unconventionally ranging from 1 Hz to 21,000 Hz, making visual assessment rather tricky.
PRO: Not only the channel tracking is tightly matched to be less than 0.7 dB from 20 Hz to 10,000 Hz, the frequency response is exceptionally diffuse-field oriented. The bandwidth is very wide too, easily reaching 20,000 Hz.
CON: There is a 3rd harmonic distortion of 2%, which is equivalent to -34 dB, at 3 kHz as the IEM hits 100 dB SPL @ 1 kHz. Such amount of distortion shall be critically audible due to the fact that 3 kHz is the frequency of which human hearing is most sensitive.
ON SECOND THOUGHT #2: The frequency response of Apple ME186LL/A becomes closer to an ideal diffuse-field target, as the source impedance increases, up to 240 Ω. However, even with addition of 100 Ω, the IEM's linearity outperforms some of the most accurate headphones, and even becomes on par with my modded Sony MH-RC. Moreover, since additional source impedance gradually decreases the 3rd harmonic distortion at 3 kHz as well, this modification is definitely recommended.
ON SECOND THOUGHT #3: The stock metal mesh effectively kills off the harshness in the high frequency range. Although additional acoustic resistance further tames the peaks, as it also decreases the bandwidth, such practice shall be done with caution.
ON SECOND THOUGHT #4: As expected, the rear vent only works as a depressurizer.
ON SECOND THOUGHT #5: The choice of ear sleeves for ME186LL/A is extremely limited. Sony hybrid sleeves, or Comply Whoomps get close to the stock quality, but other sleeves that alter the bore size/length more than those dramatically either decrease the overall frequency response bandwidth, or totally change the sound signature of the IEM. Insertion depth equally matched, above comparison data indicate the effect of longer/thinner bore. In other words, introducing additional bore resonance to the IEM works in harm's way.