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Wednesday, May 22, 2013

Earsonics SM64: An electroacoustic abomination born

Disclaimer: This pair of IEM is generously provided by Robert. Thank you, Robert!
Measurement has been carried out with a pair of stock biflange sleeves, 3 mm away from the reference plane.

Made in France, Earsonics SM64 (MSRP: €399) is a triple-driver IEM engineered with the technological know-hows the manufacturer has continously accumulated with their custom models: EM4 and EM6. Earsonics claims the IEM is capable of an "absolute control of the audio spectrum, incredible stereo image and maximum headroom, letting you crank it up without distorting the sound." Surely, the specification indicate it can output 122 dB SPL at 1 mW, even with its high impedance value of 98 Ω.

Moreover, Earsonics states, "With its new HQ crossover process with impedance corrector and drivers combination, the SM64 provides an equilibrate spectrum at any intensities that make it very musical and accurate. Having the same circumaural headphone comportment".

PRO: Nice bass & The proprietary impedance corrector retains the overall impedance characteristic quite linearly at 40 Ω.

CON: There are quite a few, thus they will be discussed separately below. 
#1: The entire frequency spectrum is disconnected in half by -24 dB @ 5 kHz relative to 1 kHz, suggesting Earsonics' crucial mistake in the crossover network design. The degree of the notch is actually worse than that of Heir Audio 3.Ai, which is about -21 dB @ 3.6 kHz relative to 1 kHz.
#2: Not only there is a substantial interchannel level mismatch above 10 kHz, but also the interchannel phase is awfully mismatched above 5 kHz, as if the tweeter driver on one channel is soldered inversely, resulting with a funky & distorted soundstage. The problem here, unless this very unit is totally defective, is actually worse than that of Novodio iHX.
#3: The 3rd order harmonic distortion barely stays below my tolerance limit of 1%.

ON SECOND THOUGHT #1: Insertion depth doesn't play much important role with SM64, as the treble is nonlinear as is.

ON SECOND THOUGHT #2: Adding a serial resistance to the IEM boosts the bass response, while slightly cutting off the bandwidth.

ON SECOND THOUGHT #3: The acoustic resistance of SM64's stock white damper is 680 Ω. Whichever the damper is used, linear distortion caused by the crossover network mismatch simply kills the overall tonal balance.

ON SECOND THOUGHT #4: Above comparison has been obtained at the reference plane.

ON SECOND THOUGHT #5: All of the issues listed above are well worth a systematic recall from Earsonics, or a lawsuit from SM64 buyers, since the measured data directly contradict what the manufacturer claims. I've never even seen/heard of a headphone designer, who would introduce a -24 dB notch in the frequency range at which the human hearing becomes the most sensitive. Here's my personal rant to Earsonics: 

If you don't know a damn about designing an electrical circuit, please go back to school.


  1. Ummm just wondering is there a patent or something to tell us more about the crossover and the impedance corrector combined together inside the drivers? I didnt know that this can be achieved.... and seems clever technique better than the TDK's approach to use external circuitry with the internal drivers' crossover

    1. Looked it up for a while, but I don't think they filed a patent for the correction unit. I am pretty sure it's a Zobel network.

  2. Is there a possibility that the product you measured is a defective unit? For a flagship, those errors seem too extreme, especially the channel mismatch (crossover design seems to be more on the manufacturer's opinion now, ie. intentional).

    1. The interchannel level mismatch is not much of a problem. The inversely soldered treble driver(only one channel) is a bigger issue. If this is the manufacturer's error, then I blame their QC capability.

    2. I suspect it could be a defective unit too IMO.

      BTW is the CSD showing that the dip at 5K is compensated?

    3. Well, the lower model SM3 has been quite notorious with build quality issues, mostly from the v1 (rectangular shell) but complaints still persist with the v2 (westone-esque shell). QC failure (I guess) is a possibility.

    4. @s: That is one of the most bogus FR data I've ever seen. Just look at the smoothing resolution! LOL

      @Roby: I'll leave the responsibility of clarification to the hands of Earsonics.

  3. I actually think they created that notch intentionally to enhance low frequencies perception. This is not surprising if they were too lazy to build a good dedicated low pass xo for the woofer.

    What bothers me more is the impulse response. You might need to try another unit and see if your friend was just out of luck or the design is actually crap.

    1. Again, the responsibility of clarification is in the hands of Earsonics, as the assessment I can come up with can only be based on what's currently available at disposal. If anybody, including the manufacturer, feels SM64 is not given a fair justice, feel free to send me a pair for another analysis!

    2. Just out curiosity, did you by any chance measure its square wave? Though this much is enough to confirm the heavily distorted response.

    3. Perhaps this is the last time I'll ever release squarewave measurements, as I find don't find them useful in assessing headphone's performance, especially when the frequency of interest is all the way up in the treble. Looking at a 10 kHz squarewave is such a joke LOL

      30 Hz:
      300 Hz: