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Friday, August 30, 2013

Astrotec AX60: A K3003 Clone from China?

Disclaimer: This IEM, which is not released in the US yet, is owned by a mutual friend of mine. Measurement has been carried out approximately 3 mm away from the reference plane with a pair of reference filter attached.

AX60 is Astrotec's new flagship hybrid IEM, featuring a dual balanced-armature transducer as a tweeter, and a dynamic transducer as a woofer. Currently, there are many hybrid IEMs, such as Audiofly AF78, Atomic Floyd SuperDarts, T-PEOS H series and Ultrasone IQ, in the market; The competition is indeed stiff. What is so special about this particular product then?

According to the manufacturer's calibration data, AX60 is precisely tuned to match the sound signature of AKG K3003, of which I consider as one of the best IEMs ever made. (but not my favorite)

The secret of K3003's articulate tonality lies in varying the size of front cavity and utilizing a tailor-fitted acoustic damping scheme. And of course, the technique is patent-protected not only in the US, but also even in the mainland China. If Astrotec have successfully reverse-engineered the sound quality of K3003 without infringing the patent, AX60 will certainly become one of the top contenders.

PRO: By 'default', AX60's electroacoustic performance doesn't even come close to AKG K3003's sound quality.

CON: There are quite a few: A time-coherence issue (phase-related) between drivers just like Westone UM3X(not as bad as this one), high distortion, bloated bass, and finally, a clearly subjectable peak, which coincides with a half-wavelength resonance of a closed ear canal, in the treble.

ON SECOND THOUGHT #1: Whether the IEM is inserted shallow or not, the problematic resonance is always present in the treble, piercing the listener's ear with extreme harshness.

ON SECOND THOUGHT #2: Although AX60 has a balanced-armature transducer implemented within, it is not hindered by electric damping as much as expected.

ON SECOND THOUGHT #3: For the sake of overall tonal balance, it might be better off to simply remove the stock filter and replace it with a small foam as a dust protection.

ON SECOND THOUGHT #4: Since the rear vent works as an acoustic low-pass filter, blocking it will tone down the exaggerated bass to a reasonable level.

ON SECOND THOUGHT #5: Here's the moment of truth: Have Astrotec really reverse-engineered AKG K3003 and created their AX60? Surprisingly, once AX60 (reference filter) is barely situated at the entrance of the ear canal, which is equivalent to the distance of about 9 mm away from the reference plane, its frequency response becomes very similar to that of K3003 (reference filter) inserted at about 3 mm away from the reference plane.

Of course, these two IEMs exhibit completely different time-domain & electrical characteristics. Moreover, this match will be completely broken even with a slight displacement of 1 mm.

ON SECOND THOUGHT #6: Apparently, Astrotec AX60 is not really a clone. The IEM is certainly tuned to match the sound of K3003, but with under a very specific condition, which can hardly be met in practice. The overall design is more of a fun college project gone weird due to misunderstanding in some of basic electroacoustic principles. Not only the IEM has an issue with time-coherence (@ 1 kHz) between transducers, but also the insertion-depth induced problem in the treble is not properly addressed.


  1. Rinchoi, I am unable to understand how none of your measurements show ear canal half wave resonances near 8khz. I am able to hear that horrible sounding resonance in all the IEMs I try besides the deep fitting etymotics.

      You can see the treble peak move downward as he moves farther from the reference plane. The resonance looks closer to 7kHz for shallow insertion, which is the experience that I've had too. My Shure's sound absolutely horrible unless I use the triple flange tips.

    2. Maybe you should use a parametric equalizer to even the frequency response out. I use EasyQ in foobar200 (with foo_vst).

    3. Hi regrepsnefpoh,
      I use Electri-Q in foobar and my rockbox parametric EQ for all my earphones.
      My question is that the 7-8k peak is not visible in any of rin's graphs.
      I get a 7.4Khz resonance in my Shure SE215, Mh1c, Philips SHE3850 and Ultimate Ears 200.

    4. You need to understand what 'ear canal half wave resonance' literally means. Insertion depth related resonance shift is already covered, just as regrepsnefpoH says.

      BTW it seems you need to insert the IEM about 10 mm deeper to reach the reference plane.

    5. "besides the deep fitting etymotics."

      You already answered it yourself.

  2. Rin, sorry for posting here.. but I need a hand from the master
    I was cleaning my IE80 yesterday and the metal mesh that covers the nozzle fell out. I tried to put it back.. but no success. So I decided to try it without the grill, and to my surprise it sounded better. Do you know if I use then without the grill could harm the drivers?


    1. Well, the grill acts as an acoustic damper, which suppresses peaks/harshness. Maybe insert a thin sheet of non-woven fiber between the ear sleeve and the nozzle, so that the driver is protected from bodily fluid & dust.

  3. Great article!

    Unfortunately when Google searching the AX60, this article is one of the first results. It seems a shame, because it genuinely may not have been an attempt to be similar to the famous ($1300) K3003. And even if it was, at almost a third of the price, It's still a great IEM.

    Thanks for the info!

    1. Thnx for the words, White. I'd purchase a pair if it was below $100..