Acoustics Audio IEMs Knowledge Rants Thoughts Universal-Fit

Rant: Audio-Technica ATH-IM02 vs. ATH-CK90PRO MK2

Editor’s Note: Not so much a rant; more bemusement than anything else.

Audio-Technica‘s new series of enthusiast-oriented IEMs was introduced a few months ago (last November) to great fanfare.

Other than the 50th Anniversary products (that included the ATH-CK100PRO) released a couple of years ago, it’d been a very long time since the Japanese audio stalwart last introduced a entirely new lineup of in-ear products.

For many enthusiasts, memories of the legendary ATH-CK10 still lingered in their minds, so when Audio-Technica came out with six new models, complete with a proprietary removable cable system and an utilitarian design language, people took notice, and expectations were high.

Interestingly enough, Audio-Technica decided to go in a different direction, sound-wise, with the new IM series of in-ear monitors.

These are not your older brother’s Audio-Technica earphones. The new series is warmer, smoother, and less peaky overall. Clearly, the “Always ListeningAudio-Technica has been responding to customer feedback, and the new lineup put Shure, Westone, and Ultimate Ears squarely in their sights. Over the past few years, western companies have launched a clear offensive on the eastern market — most notably, Shure has been launching all its major product announcements in Japan, while Ultimate Ears has opened up self-managed boutiques in China. The IM series was Audio-Technica‘s response — they clearly wanted to protect their home turf.

To ATH devotees, however, the new overall sound signature was met with mixed results. Users were concerned that Audio-Technica had lost its core sound — you wouldn’t want to eat your Rice Krispies if it didn’t have the snap, crackle, and pop, would you?

Out of the six new models introduced, the ATH-IM02 has gained standout recognition as perhaps possessing the best value of the bunch, by users commenting on forums and around the blogsphere. Users claimed that the IM02 was the airiest of the bunch, imparted the widest soundstage, and still preserved the Audio-Technica sound. They made it out to be the best thing since sliced bread.



  1. Interesting article. Agreed about the CK90 series being overlooked, though I haven’t tried them. Have you managed to try the ATH-IM03 as well?

    Also, what do you have to say about the bass response of the IM02 (and 03, if you’ve tried it)? I’m very wary of IEMs with a lean bass that ends up being misrepresentative of the authentic weight and fullness of the music and instruments.


    1. Yes, I did try the IM03. It is similar to the former Audio-Technica flagship CK100PRO, but with a less finicky top end. The IM03 is slightly more robust in the low end than is the IM02.

      However, the IM04 will definitely impart the deepest bass out of all the IM series. It uses two very high-quality vented woofers that allows its bass to be set apart from the rest. However, in terms of tonal balance, it is also the darkest of the lot.

      My recommendation would be to give anything that seems initially “lean” in the bass region a chance for about a week, listening to it exclusively. That week will allow you to get used to the signature, and allow your brain to readjust. It’s true that certain earphones are unable to transduce weight as authentically as others, but the effect is perhaps less pronounced than what most people think.


      1. Thank you, that definitely increases my confidence in the IM03. The IM04 is definitely beyond my budget, and I also don’t want a DARK IEM.

        Here’s a bit of background, if it matters. I’d appreciate if you could help me out.

        I’m a musician and music producer. When I’m at home working, I have my studio monitors (Yamaha HS7) and headphones (Beyerdynamic DT880 Pro) for all listening, and I love them both. That is my general reference point for neutral sound – NOT lacking fullness, realistic weight and body in the bass. It seems most ‘neutral’ IEMs however, suffer from a lack of the above, and I understand the IEMs seem to need to be tuned with a gentle-to-moderate, but controlled boost in the low-end to achieve a similarly realistic representation of the bass regions.

        I own a VSonic GR07 MkII that I find to not represent the general low-end to my satisfaction. My production references, and my own mixes, sound thin, realistic fullness and body in the low-end, when listening through the GR07 MkII. EQing helped a bit, but I want to stay away from EQ as far as possible. I also found the treble to be uneven, spiky and a bit unrefined.

        Within a budget of say, $300, I’m looking to find a pair of IEMs to give me a balanced, fairly neutral sound, but with that realistic body, weight and fullness in the low-end. Which will probably imply the IEM having a general low-end boost, which I am okay with. I definitely do not want bassy IEMs though. Balanced but with a full-bodied, realistic low-end. I also would like the top-end to be smoother and more refined, without peaks and resonances (to whatever extent is achievable in my budget).

        Isolation is a priority, as these are strictly for use while commuting. Also would like an airy, open, large soundstage, with good imaging.

        Is there anything in your experience with IEMs that will give me these? What are your recommendations?

        Thank you!


      2. Yes, for IEMs there’s a “missing 6 dB” in the bass response that usually prompts IEMs to be tuned with more bass, but the discrepancy is more of a lack of “training”, so to speak. Because IEMs are generally a “closed” system with your ears, psychoacoustics plays a big part of the equation, and thus accurate monitoring with IEMs requires you to “hear” the bass signal, rather than “feel” it, and if you’re able to decouple the two, it really helps you not need bassier IEMs. However, most people find this psychological decoupling to be a chore (because it must be goal-directed), so most manufacturers just turn up the bass, as most people are “all about that bass” anyway.

        One disadvantage that you have with the GR07 is that it is a dynamic driver IEM, and the venting prevents it from being as isolating as it can be. I am surprised by your statement that you find the GR07 too thin-sounding, however. It could be that you’re hearing the treble harmonics, and attributing its sharpness (the GR07 tends to have somewhat sharp and defined treble) to overall thinness of body. In a quiet environment, the GR07 will probably sound a lot more full-bodied.

        Thus, my recommendation would be to get a pair of budget custom IEMs. It sounds ridiculous, but since you’re a musician, investing in a pair is worth it — my default recommendation for any other kind of listener would not shoot straight to customs.

        Granted, they’re not as convenient to put on and remove, and have poor resale value, but you’ll find that the added comfort and isolation will get you to be able to hear the details better than ever before — don’t worry about the driver count (it should never be considered an indicator of sound quality when considering any balanced armature IEM, despite marketing — more drivers means lower distortion, more input headroom, and room for more tailored frequency responses, but most dual drivers do a good enough job).

        Keep in mind that you’ll also have to go to the audiologist to get ear impressions, which will run you between $35 to $100, typically, unless you attend a trade show like NAMM and get them done with the company itself.

        Also remember that Thanksgiving is coming up, and many custom IEM companies will be discounting their models by quite a bit. 1964Ears typically slashes their prices by quite a lot, and the 1964-V3 will likely be slashed into a price range that you can consider. Noble Audio holds a sale as well, but the products that most suit you are perhaps in the higher end of things (8C, K10). The Ultimate Ears UE4 Pro is a great choice, though it’s typically not discounted and only comes in clear. JH Audio does hold Black Friday sales, however, and the JH5 should be a great starter monitor.

        The extreme budget end for CIEMs is with Perfect Seal Labs in Kansas, and Fisher InEarz in Florida. The Perfect Seal Silver and the Fisher IE-P250 both the Sonion 1723 AcuPass dual driver, which is a great setup for value priced IEMs. Both should come in at a raw price of less than $300, which is absolutely affordable. Granted, I’ve heard neither, but it has been well-received by other reviewers that have heard them, and I know the capabilities of that 1723 driver. It’s difficult for that driver set to sound bad.

        For silicone monitors, currently my only recommendation would be Poland’s CustomArt, as they really hit the sweet spot with respect to value and balanced sound signature. The Music Two (read shotgunshane’s review: is a truly great all-arounder; both shotgunshane and I bought a pair. It’s accurate enough for monitoring, but is really able to express music really well also. It has energy and depth in the low-end, but does not get bloated. It’s brighter than a conservative monitor tuning, but pulls back when others can get really harsh. It’s truly an excellent value. It’s near the ceiling of your budget, but I’d still recommend you give Peter an inquiry. He’s a personal friend, but I can state objectively that his products are excellent.

        If you’re not ready to take the custom plunge, EarWerkz is slated to launch their “Project Supra” next week on Kickstarter ( Supposedly, it is their EP-2 model in universal form, but official details have not come out yet. From his listen, shotgunshane highly recommends this model (read about his experience here:

        Keep in mind, however, that the universal fit might not necessarily be perfect. As the universal shape has not been determined as of yet, it’s difficult to deal out a definite recommendation. Of course, you could go for the custom version (which also has a slightly more bass-enhanced EP-2+), which is currently on sale until the end of the year, and costs just a bit more than the IM03.

        Slightly higher up the price food chain is the German InEar Monitoring SD2. It was mentioned in this article as being extremely similar to the Westone 2/W20, as well as the IM02 on account of all of them having the same exact dual driver GQ unit from Knowles; however, with the benefit of a good fit (the fit is near perfect for an universal IEM), the bass gets fleshed out really well. Expect a similar timbre and midrange presentation to the IM02, but with better rounded bass, as the SD2 isolates as well as any custom IEM, given the right fit. Read my quick impressions on them here:

        Honestly, your ideal in terms of sound signature would probably be something like a FitEar MH334, but that’s almost certainly out of your budget, I’m sorry to say.

        This is just a primer. Don’t hesitate to let us know if you have further questions trying to narrow things down. My recommendation for you is to go for a pair of CIEMs, because they will come in handy for your music career, though if you’re not ready, we’ll continue to help you with alternatives as well.


      3. Thank you very, very much for that detailed, painstakingly elaborate reply. I really appreciate you taking the time to write that out!

        Unfortunately, custom IEMs are not what I’m looking for at the moment, for multiple reasons – first, I only use IEMs while performing when I am absolutely required to, because I dislike the presentation of in-ear monitoring while performing, as opposed to using regular stage monitors. So the appeal of custom IEMs for professional use doesn’t draw me all that much. Second, I live in India, and the additional cost of shipping impressions overseas is something I’d prefer to avoid entirely.

        So for now, I’m looking for a set of universal IEMs.

        About the GR07 MkII, I’ve used them in studio-quiet environments as well, and I always find the low-end lacking in the expected, natural weight and body, both in the timbre of bass instruments and percussion, and in the general presentation of the low-end of mixes. As you said earlier, this can be attributed to the missing 6db effect, which I’ve read about earlier. I also sensed a general mid-bass dip in the response of the GR07, which is a definite contributor.
        This lack of fullness is also possibly a result of the kind of bass decay that a very fast driver might possess, though I haven’t looked at the measurements and charts of the GR07 MkII in much detail, to confirm that.

        Now something like the HiFiMan RE-400, I found more natural in its presentation of the low-end. I haven’t directly compared FR charts of the RE-400 and the GR07 MkII, but the RE-400 did seem to have a fuller, and to my ears, more natural mid-bass, which lent a more realistic body to instruments and sounds in the bass region. The main drawback of the RE-400 was the gently but noticeably recessed top-end, which took away some brilliance from the representation of cymbals and some air from the overall presentation.
        To my ears, the RE-400’s frequency response can be summarised as ‘neutral with a gentle shelf lift in the low-end, and a gentle shelf dip in the upper treble’.

        What I’m looking for is roughly something not far from the RE-400, but without the gentle dip in the treble. In a universal IEM. Close to neutral, but with a mild lift in the mid-bass and below, and with a neutral, but clean and well-behaved top-end.

        Any universal IEMs within the $300 dollar mark or so that come to mind?

        Once again, I greatly appreciate your replies and their thoroughness. 🙂


      4. I understand your perspective on customs; as a person whose day job is in healthcare, however, I merely want to remind you that hearing preservation is paramount. With that said, universal IEMs can help with that to a certain extent.

        Living in India will certainly complicate things. Unfortunately, the market for higher-end earphones is simply not very mature there.

        The RE-400 is great for balance. The XBA-A3 (not H3) that I recently heard will probably fit your bill, but its fit doesn’t lend itself any favors when it comes to isolation.

        The Ostry KC06 and KC06A might be worth considering, as they’re pretty affordable (but sound great). Drawback is isolation, which isn’t terrible, but no better than the GR07.

        I hesitate to recommend products that I haven’t personally heard, but it might be worth considering the Brainwavz R3. It should have what you’re looking for when it comes to sound. The only questions are comfort and isolation.

        The DUNU DN-2000 is also a worthy choice. The sound will be to your liking, but while I personally had no issues with fit or isolation, others have.

        Out of the “big company” offerings, the Logitech UE900 is one to consider.


  2. Hi there! Just came across this article recently and I have some questions that I hope you can clarify.

    According to the article, it says that both the ATH-CK90PRO and IM02 actually shares the same driver, and that is why the measurements share some kind of resemblance. Even the Westone 2 and InEar SD 2 gave similar measurements and the reason is that they all use the GQ-30783.

    The reasons given to explain the technical specifications and differences in subjective listening (in the context of the SD 2 and W2) is that there is an “increased build quality, tighter fit rate, and isolation” for the SD2 as compared to the W2. However, I am just confused as to how build quality actually affects the technical specifications. Shouldn’t the drivers be the only factor that affects sensitivity and impedance? I am new to this so please be patient… 😦

    SD 2: Driver: Dual BA | Imp: 40Ω | Sens: 119 dB | Freq: 20-18k Hz |

    Westone 2: 117 dB SPL @1mW Frequency Response: 20 Hz -18 kHz Impedance: 33 ohms @1kHz

    Also, from what i understood from the article (correct me if I am wrong), it seems that if I were to send both the ATH-CK90PRO and the IM02 for re-shelling into custom IEMs, (suppose that the ear molds sent were identical, and the manufacturers managed to produce identical CIEM shapes, cables are the same too), will the two models now sound exactly the same? And applying this re-shell to the W2 and the SD2 too? Will all 4 of them sound the same now?
    If that is true, it definitely isn’t wise for SD2 users to go the custom route since they could have just got a W2 and re-shell it at a lower total price.

    The point I am driving at is that: are there really no difference in the drivers used in all 4 models? Maybe the companies have done some tweaks (to driver or crossovers etc) that made a change in sound quality? I understand that the housing of the IEMs will affect the sound quality, but is it really true that it is the only factor that that caused all the IEMs mention above to sound different?

    Once again, I must say that I am rather new to these topics and am still learning so please be patient, if these questions sound amateurish… Thank you for your attention!


  3. I’ve tried a pair of CK90PROMK2 and liked them, but ergonomics and the actual price tag of the seller is worse than IM02. I have no opportunity to try IM02 but can order them. Would you say they sound close(similar) enough to order IM02 without listening them if I liked mk2?


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