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AKG K3003 Universal IEM Review: Challenger to the Custom IEM World?


AKG, part of Harman, is well known in the pro market for making quality products that can be found in studios throughout the world (and even in Skullcandy pictures!).  Harman has other brands that are more consumer focused, but AKG does have some consumer products including the ultra-high end K3003.  Hand made by AKG in Austria, the K3003 uses a dynamic bass driver and dual balanced armature drivers for the midrange and treble.  There are interchangeable tuning ports (filters) that change the sound signature as well as a three button Apple compatible inline mic/remote.


While I primarily review custom IEMs and associated equipment, I have been asked many times how the K3003 compares with custom IEMs as there are people that don’t want to go through the steps to make a custom IEM.  Luckily, I do get to hear many universal IEMs in addition to my custom IEMs, and when I had the opportunity to borrow a K3003, I of course said yes!  With a price tag that exceeds that of most custom IEMs, even the top offerings from most companies, at $1500 price tag (introductory price of only $1300), I really wanted to hear how special the K3003 really is.  So, stepping away from my typical custom IEM review and glove like fit of a custom IEM, I threw on some ear tips and jammed them into my ears.


But first, let me explore the difference between custom IEMs and universal IEMs, especially ultra-expensive universal IEMs.  Since custom IEMs are molded of your ears, ear impressions that need to be provided to the manufacturer, which then needs to spend the time to make them.  With shipping times this can take anywhere from two weeks to several months.  Universal IEMs only require a purchase, and if online, a short period of time before you receive them.  With custom IEMs, there may be fit issues requiring the CIEM to be sent back for a refit while the stock ear tips hopefully fit you well, although you may need to buy additional ear tips to get the best fit.  The results of the wait usually are an improved comfort and isolation from a custom IEM.


And let’s not forget resale value.  What if you don’t like the sound, grow tired of it, or need to sell for whatever reason?  A custom IEM will need to be remolded for the next persons ear, which cost money and time while not giving a guarantee of the same sound.  Sure, there are some companies that have policies that actually make it easy to resell, such as Heir Audio, but the vast majority doesn’t.  It is very important to know your preferences and what you are getting before buying with a custom IEM, which is a very large part as to why I have reviewed as many custom IEMs as I have.  Universals usually have a 30 day return policy, and even after that typically have a better resale value than a custom IEM.  Both typically do not have the warranty when ownership is transferred, so that could dramatically affect something with a high price such as the K3003, but time will tell.  So, there are many people that want the instant gratification and/or don’t want what they deem as risks getting a custom IEM.  At least there is something for everyone!


The inline mic/remote of the K3003 will work with Apple devices as described here, however they don’t mention that the 3-button Apple remote won’t work with all Android devices, and if it does, only the middle button will work from what I know (let me know if I am wrong).  The K3003 does come with an adapter for use with phones and devices that aren’t compatible with the mic/remote or devices that aren’t compatible with the 4 pin plug.  Given the price, the lack of a detachable cable is a disappointment since most IEM failures are due to the cables and/or inline mic/remote.


However, my cable issues have been somewhat suppressed upon seeing the K3003 since the build quality is amazing, as it should be for a product at this price.  The stainless steel housing and accents instills confidence, the cable feels tuff and built to last, and the remote looks very robust.


Of course, with something this good looking and with anticipation of high performance I tried them with the largest stock ear tips.  No seal resulting in poor bass.  How about over-the-ear?  Still a no-go for me.  Medium tips, uh, they don’t work either.  So, I have a $1500 earphone that doesn’t give me a good seal.  Luckily, I have amassed a large collection of ear tips and spent several days switching between different ear tips including very large single flange, HiFiMan bi-flanges, and triple flanges, as well as everything else that would fit on the nozzle.  I ended up with the triple flange tips for a combination of comfort and sound quality.  I did have a very positive impression upon first listen (they had 80 hours on them when I received them).  Comfort levels aren’t the best for me due to the shell protrusion for the cable, but I can find a sweet spot in my ears that allows me to wear them for a few hours at a time.


So, the beginning of my first universal IEM review in over a year and it is off to an interesting start.  But, it is turning out to be a fun review for me and a good change-up!


How to Order, Warranty, Options

Available at many retailers including J&R and Sound Earphones.  The price is going up from to $1500 soon from the $1300 current cost.  The K3003 has a 2 year manufacturer’s warranty.



Universal fit with a stainless steel shell and permanent cable utilizing a 5.5mm nozzle diameter.  Drivers consist of a single dynamic bass driver and dual, compound balanced armature drivers for both the midrange and treble in a 3-way configuration.  There are three interchangeable filter tunings named Reference Sound (installed), Bass Boost, and High Boost.  The High Boost port has no filter while both the Reference Sound and Bass Boost ports have filters that are in line with the balanced armature sound tube.


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The K3003 comes with a carrying pouch, airplane adapter, adapter cable, 3 sets of tuning ports, and 3 sizes of ear tips.  I am not a fan of the carrying pouch as I found it time consuming and difficult to wrap the cable and try to get the earphones in the pouch properly.  Maybe if I used the pouch consistently it would get easier to use, but I used a different zipper pouch.  The ear tips are designed to fit the K3003 and only protrude a tiny bit beyond the tip of the filter, so I can’t get a seal with them due to my large ears.  More later in Fit, Seal, Tips, and Comfort below.


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The cable is permanent with an Apple compatible inline microphone and 3-button remote on the right channel between the Y-split and earphone.  From the 3.5mm 4 pin plug to the Y-split, the cable is nylon wrapped and rubber coated from there on up to the earphones.  The Y-split is very small and made of stainless steel, as is the cable cinch.  The cable cinch is permanently attached to left side of the cable after the Y-split while the other side is free to be attached above or below the inline mic.  The cable performs quite well with good tangle resistance and no microphonics, but is not quite as ergonomic as the stock cables most custom IEMs come with, however it is thicker and gives more confidence.  The cable has a stiffness to it that doesn’t affect use but will control how it lays, which I noticed while taking pictures, which indicates the strength and durability of the cable.


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Build Quality

The build quality of the K3003 is top notch as stainless steel is a very hard and durable material, and the cable, mic/remote, plug, Y-split, and housings all feel extremely durable.  Of course, as a loaner, I did treat them well, but they do seem to be built to last.


Fit, Seal, Tips, and Comfort

The K3003 can be worn cable up or cable down and I tried both configurations using quite a few types of ear tips in addition to the stock ear tips before I settled on the triple flange ear tips since I couldn’t get a seal with the stock tips that didn’t cause severe discomfort.  The issue with the stock ear tips is that they barely protrude past the nozzle, and my larger ear canals need a deeper insertion to achieve a seal.  I also used an over-the-ear wear style for my testing due to the insertion angle.  This did require me to position them in a specific way to avoid the housing bulge, where the cable enters the housing, to cause discomfort.  In addition to the triple flange tips, the Sony hybrids and HiFiMan large bi-flange tips also worked; basically anything that sat further down the nozzle and would stay put allowing for a deeper insertion.

I noted some sonic differences between the triple flanges and Sony hybrids, which sounded similar to the stock tips that I couldn’t use, and the triple flange tips.  The triple flange ear tips have a brighter presentation with smoother treble as well as more deep bass quantity due to the better seal.  I would have used the Sony hybrid tips, but had some comfort issues for extended wear, so ultimately I went with the triple flange tips.





The isolation is on the low side in comparison with my custom IEMs and a bit lower than my SM3.  If an average acrylic shelled custom IEM is a 5 of 10, then the AKG is well below, around a 2.5/10.  Of course, ear tips and fit will affect this, but for my large ears and need for aftermarket tips, the isolation is surprisingly lower than I am used to with universal IEMs.



The K3003 received 100+ hours of burn in as is customary before I do my serious listening.  You can read about my technique here.  Since it was already burned in before I received it, I have no initial thoughts other than out of the box I knew it was a competitor.  For comparison I used the Hidition NT-6, JH Audio JH16, Ultimate Ears In-Ear Reference Monitor, Spiral Ear SE 5-way, Earsonics EM4, Starkey SA-43, Earsonics SM3, and Wan Xuan i9pro.  Click here to see my multi-custom IEM review thread.


When just listening to the K3003, they are a mesmerizing pair of earphones, and I do have to say they are the best universal I have heard.  But, when I jump into critical listening mode, the K3003 isn’t perfect, and there are some issues that jump out at me.  This is not to say the issues will jump out at you, but they do to me because I am a frequent high end custom IEM user!


The K3003 comes with three different tuning ports, and they do make a significant difference to the sound, essentially giving you the option to tune them to your preferences.  The Reference Sound port is installed out of the box, and there are Bass Boost and High Boost ports.  The spare ports are stored in a labeled, threaded stainless steel plate.


High Boost port:  It appears the high boost port is just a grill that doesn’t filter the balanced armature.  The treble is the most natural sounding, not having the peaks of the Reference port nor the treble roll off of the Bass port, but the overall sound is not as tonally natural as the Reference Sound port.  It is, of course, the brightest of the three, but the bass and midrange remain untouched from the Reference port. The upper midrange and treble are pulled a little forward compared with the rest of the spectrum, however this port is not unlike many other IEMs such as the Ultimate Ears In-Ear Reference Monitor or the EX1000.  Technically, the High Boost port performs a bit better than the other ports as it has the most coherence across the frequency spectrum.


Reference Sound port: While the Reference Sound port provides the best frequency and tonal balance of the three ports, it also has the most technical issues due to what sounds like driver matching issues as well as treble peaks.  Music is presented with balance from top to bottom, not pushing any part of the spectrum forward or backward, although there is a dip in the midrange that is most likely due to the crossover point of the dynamic driver and BA driver as well as the filter lowering the BA output in this region.  This issue isn’t unique to the K3003 as my CIEM hybrids have this issue to some extent as well, and I can forget about it when I am just listening to music and not critically listening.  Overall, this port is my preferred port due to the tonal qualities, even though it has the most technical issues.


Bass Boost port: Once the shock wore off from the steep and prominent treble roll off, the Bass port gave some warm, smooth sound.  The bass is pulled forward from the rest of the presentation, or actually the midrange and treble are pushed back, opposite of the High Boost port, creating a dark presentation.  It is a non-fatiguing sound, not that the K3003 is fatiguing with the other ports.  The feeling I get when using this port is that of being just outside a concert hall where I can still hear the music loudly, but much of the treble energy didn’t make it out the door.

Bass: The dynamic bass driver of the K3003 can recreate a full and impactful experience while never overpowering the rest of the spectrum regardless of the port used.  Texturing is good and bass notes sound natural and realistic with good weight in the lower registers and a strong ability to rumble.  As is typical of dynamic bass drivers vs. balanced armature bass drivers, the bass exhibits good sub-bass rumble while lacking the speed and control of the BA drivers.  AKG tuned the K3003 with a near perfect balance to the bass region that results in an extremely positive experience that is weighty, fun, and rich with great quality and performance.


Midrange: The lower midrange sounds very natural and realistic while the upper midrange changes depending on which port you use, changing the tonal balance and realism.  With the Reference port, the midrange is very natural, with beautiful vocals and realistic note thickness while the High Boost port allows the unfiltered sound from the balanced armatures to come through, which, while not peaky, does give an upper midrange boost resulting in a presentation that is a bit brighter and more forward.  The Bass Boost port cuts the output of the upper midrange on up, resulting in a darker tonal balance.


With a direct comparison with many of my high priced custom IEMs, there is a coherence issue in the midrange where the dynamic bass driver and the midrange driver crossover that is most noticeable with the Reference Sound port.  With the High Boost port the issue is much less noticeable, and with the Bass Boost port it is suppressed even more as it is very hard to hear when comparing with my single dynamic driver custom IEM, the i9pro.


Treble: Carrying over from the midrange, the ports affect the sound quite a bit in the treble region.  The Reference Sound port introduced some peaks that aren’t present with the other ports, although the overall quality is still good.  With the High Boost port, the quality of the treble is improved as is the brightness, while the Bass Boost port severely cuts back on the amount of treble, pushing it far back from the rest of the presentation.


Presentation: The K3003 has a very nice note presentation and overall the sound signatures have their place for various sound preferences of the owner.  Bass notes are full while the notes presented from the balanced armature drivers are a bit different in the midrange on up, however the matching is better than other hybrids I have heard.  Spaciousness is good for a universal with nice height, width, and depth, but does fall behind most of my higher priced custom IEMs.  There is a high level of transparency, but it fluctuates with the ports, as the Reference Sound port performs below the other two due to the coherence issue.  Clarity is excellent and detail levels are quite good, performing about midway in the high end custom class.  While not lacking speed, the K3003 doesn’t give a sense of speed like a brighter BA CIEM due to the note thickness, but does have a nice, natural sounding note decay.


Comparisons: Since the K3003 has 3 sound tuning options, the filter that resulted in the closest sound to the comparison IEM was used.

Hidition NT-6: I used the High Boost port for this comparison as that port is the closest match to the bright sounding NT-6.  The K3003 has a more prominent bass presence and a comparatively mid-forward presentation vs. the smoother, more coherent, and more transparent NT-6.  Soundstage size in all directions is better with the NT-6 and is presented in a more cohesive way.  The tone of the NT-6 sounds more natural in direct comparison.


Bass weight is higher on the K3003 throughout the bass region, making the deepest registers rumble with more reverb as well as add more warmth to the presentation, but the NT-6 can recreate rumble, but always at a lower level.  The more laid back midrange has better clarity with the NT-6, but the K3003 does have impressive clarity.  The upper midrange and treble of the NT-6 is more prominent than the K3003, but the quality is also higher, which also has the downside of being less forgiving of poor mastering.

The NT-6 slices through your music with clarity while presenting in a bright and light way, never seeming bass heavy at all while the K3003 has a better balance across the spectrum to go with a fuller sound.  The NT-6 can easily be used for mastering, and many audiophiles will love the sound signature, but the K3003 is aimed squarely at the high end consumer market.  Depending on your perspective, preferences, and needs, either can be a great buy.


EM4: The Reference Sound port was used for comparison.  The EM4 presentation is airier and more spacious, but with some tracks the EM4 sounded a bit too spacious for its own good in comparison while other times the K3003 sounds a quite small in comparison.  Even though the K3003 has a dynamic bass driver, the EM4 keeps up with the K3003 in the bass quantity department including sub-bass rumble, but also presents the bass with more control, especially when there is a lot of sub-bass.  Clarity is close, but the EM4 wins out more often than not.  The actual presentation of these two is different as the EM4 is mid-forward while the K3003 has a more linear presentation across the spectrum.  While I have had some coherence issues with the K3003, they weren’t bad in comparison with the EM4.


These two are similar enough to each other in to be considered competitors, but the EM4 will give you a more dynamic, spacious, and controlled sound vs. a more balanced and laid back sound.


SE 5-way reference: The Reference Sound port is the closest match in terms of frequency response, however the High Boost port is the closest in terms of performance and was used for comparison as the Reference port sounds smaller and disjointed in comparison.  With the High Boost port in the K3003 sounds artificially bright in comparison and lacking a layer to the sound that is presented with the 5-way.  While the K3003 is very clear, the 5-way has a natural clarity to the sound from the higher resolution and a better presentation focus within the soundstage.  The treble is moved much closer to the front with the K3003 with the High Boost port, and the midrange is also more forward, but not to the same extent.  Even though the cohesion of the presentation is better with the High Boost port, it still lags behind the 5-way.


Bass quantity is similar between the two, and both have good sub bass rumble, however the 5-way can output more bass both in tactile rumble feel and punch with better control, if only with higher end sources, but the K3003 is no slouch.  The midrange of the K3003 is sweet, but the 5-way is more liquid yet detailed.  Treble quality also falls behind that of the 5-way.  After receiving my replacement 5-way, the treble of the K3003 falls further behind the 5-way treble quality.


Considering the K3003 is actually more expensive* than the 5-way, at least in Europe, and considering the 5-way has a detachable cable, I find it hard to recommend the K3003 over the 5-way, especially if you are going to use the Reference Sound port on the K3003.   There are reasons to get the K3003 though, including the desire to change sound signatures, less isolation, and retain a higher resale value as well as phone functionality, but since the 5-way has a detachable cable option, you should be able to get a phone compatible cable in the near future.  While I can easily listen to the K3003 all day (or, at least until my ears hurt), I find it difficult after listening to the 5-way.


* Depends on where you are and how long the introductory price lasts as the 5-way with detachable cable can be a bit more expensive.


JH16: The K3003 sounds fairly close to the JH16 with the High Boost port in, however the JH16 sounds more coherent from top to bottom and has a slightly smoother presentation.  I wanted to note that with the Anedio D1 DAC, the JH16 sounded a good deal better while with the iPod->Portaphile the K3003 sounded better.  While the tonal balances are similar, the K3003 is more mid-forward than the JH16 and has less upper midrange presence, but with an emphasis that spans a wider frequency range.  Soundstage layering of the JH16 is better and the presentation is wider although the K3003 has more front-to-back depth to the presentation. Focus of the presentation is better with the K3003, and while the JH16 is naturally slightly clearer, the better focus of the K3003 can lead to a clearer and more articulate presentation as the clearer presentation flip-flopped depending on the track.  Detail levels are similar, but the JH16 is more resolving of instrument details.  Tonally, both sound a bit different, but neither sounds more natural than the other.


Depending on the source, either can sound more bass enhanced and powerful.  For example, from the D1 the JH16 bass is more emphasized, powerful, deep, and reverberant, but with my iPod -> Portaphile the K3003 flip flops.  The midrange is pretty close in presentation, but the JH16 sounds faster and more precise.  In the treble region, the JH16 has more sparkle and emphasis with a more in your face presentation and a smoother, more natural sounding note.


Both are good performers for their respective audiences, with the JH16 offering a bit higher technical performance and close to the same bass punch.  The JH16 would probably be a better fit for electronics genres and many vocals while the K3003 would work well with acoustic tracks.


SA-43: The SA-43 sound with both the bass boost and presence switches on is between the Bass Boost port and the Reference Sound port on the K3003, but closer to the Reference port.  The K3003 is either brighter or bassier depending on the port, and with the presence switch off the SA-43 is more laid back than any port with the K3003.  The first thing that hit me comparing these two other than the required driver power differences was the difference in space, as the SA-43 has a much more expansive soundstage.  Detail levels are similar, however upper midrange/treble details are much easier to hear with the K3003 due to the brighter presentation of the Ref port, however with that port the weaknesses are easily audible, as the midrange sounds recessed and the coherence across the frequency spectrum doesn’t sound good in direct comparison.  The SA-43 is also smoother in the midrange on up, leading to a more transparent sound.


In general, the K3003 has more bass emphasis, however the SA-43 isn’t too far behind in reverb and has more texturing and bass detail. While the soundstage of the K3003 is smaller and sounds a bit mid-forward because of that, a part of the midrange is actually recessed in comparison with the SA-43, which is what creates the frequency spectrum coherence issue.  But, the opposite can be said in the upper midrange as the SA-43 sounds recessed from there on up in the spectrum.  However, with the BB port, the K3003 becomes smoother, although still not on par with the SA-43, while becoming darker.


These two are very different IEMs for different situations.  Both have adjustments and are in-ears, but the similarities pretty much end there.  The SA-43 is much harder to drive, needing a volume of about 26 on my D1 DAC to equal the volume with the K3003 at 4!  One is customized, the other isn’t which results in what seems like at least a 10 dB isolation difference.  And the sound; one is smooth, spacious, and laid back due to the upper midrange/treble presentation while the other is more up close and personal with a brighter (2 of the 3 ports at least) presentation.


UERM: Using the Treble Boost port to get as close as possible in sound, the UERM is still leaner and brighter than the K3003.  The presentation of the K3003 is more mid-forward while the UERM is more spacious but distant/larger sounding.  The detail level of the UERM is a bit better than that of the K3003 along with a more upfront presentation of detail, which results in a much less forgiving sound for poor recordings with the UERM.  Clarity levels are similar, but the UERM has a bit more clarity as well as being more transparent.


The dynamic driver provides more bass emphasis and capability, especially in deep bass rumble.  With a smaller and more mid-forward presentation, the K3003 brings the singers closer to you, but the overall presentation of space isn’t as deep or 3D, although it is immersive due to the mid-forward presentation.  Treble is not too far off, at least up to 13K while the UERM remains flat and extends a bit further vs the K3003 which starts to roll off resulting in the UERM sounding brighter.


Overall, these two are somewhat similar in presentation, however they do serve much different purposes.  From a sound perspective, the UERM lacks low end rumble and sense of power the K3003 provides with bass heavy genres but does offer a bit more detail with a brighter, more transparent sound.  Of course, you can change the sound with the K3003, but regardless of the port the UERM is brighter, more detailed, and transparent than the K3003.  Technically, the K3003 isn’t too far behind, but the K3003 offers many things the UERM doesn’t from the simplicity of just buying it vs having to get a custom IEM made to better bass power and capability.


i9pro: I compared these two for fun since these two aren’t competitors in price or sound signature, but they do have two similarities: the dynamic driver (I know, the K3003 also uses BAs) and the straight plug!  I used the Bass Boost port with the K3003 for comparison.  The K3003 was difficult to listen to after the i9pro was in my ears as the i9pro presents the music with a more natural tone as there is something odd in the upper midrange/treble area taking away from the naturalness.  The i9pro is much more spacious than the K3003 and has quite a bit more bass power, rumble, and emphasis without lacking control.  The capability of the i9pro is impressive and should please the most demanding bass heads, however the does present more detail with better clarity and a more reasonable amount of bass for non-bass heads.  I will end it here since most people won’t be deciding between one or the other.


SM3: The K3003 is a much different animal, taking some of the virtues of the SM3 such as a liquid presentation with good 3D space, but the SM3 is a bit more liquid and has a bit more depth to the presentation, although less width and poorer imaging.  The K3003 handily beats the SM3 in clarity and bass capability while having a more natural sound (with the Reference Sound port).  The midrange of the K3003 is forward, but not as forward as the SM3, while presenting instruments more concisely and vocals in a more natural, sweeter way.  While it did best the SM3 in many ways, it wasn’t as lopsided a victory as I had expected for a product that cost $1K more (close to 4 times the price).  From a form and fit perspective, the SM3 won as it is more comfortable in my ears.


Volume performance: Some dynamic drivers kick in at very low volumes while others take more juice.  The K3003 is in the category of the latter, as I had to turn the volume up to a low-mid level to get the bass to become reverberant and full.  This isn’t unusual, and the performance was at least as good as most balanced armature driver CIEMs.  At louder volume, which I could only listen to for about all of 3 seconds at a time, the presentation wasn’t quite as clean and clear as at lower volumes.  This could be heard ever so slightly at moderate-high volume levels, so performance is good if you plan on keeping your hearing and using lower volume settings!



Sound Summary: The K3003 is a fantastic universal IEM with sound signature options.  Bass is full, controlled, textured, and refined while the rest of the spectrum is smooth and detailed with very good dynamics.  The Reference Sound port has the most natural sound to my ears, but there are some frequency coherence issues as well as issues with peaks in the treble.  The High Boost port technically is the best of the three with a brighter sound and smoother treble, although it is brighter and doesn’t have the same tonal quality as the Reference Sound port.  With the Bass Boost port, the K3003 becomes a bass heavy IEM by pushing back the midrange and treble, but it still retains the high level of technical performance.  The level of performance is quite good, although it does fall short of the CIEMs that come close in price.


Source matching


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Portable Sources, DAPs

Clip+: The Clip+ isn’t bad at driving the K3003, although the biggest weakness is the size of the soundstage, which is smaller than with the iPhone and ROCOO.  Detail levels are quite good from the Clip+ and while bass isn’t quite as powerful or controlled as with higher end sources, but it isn’t bad. 5/10

iPhone 4S: More bass punch compared with the Clip+, however not as much control.  Spatially, the 4S recreates a larger space, and while detailed, it is a bit behind the Clip+.  Dynamics are also a bit behind the Clip+.  4.5/10

RoCoo Power: The ROCOO Power transforms the K3003 bass from a powerful performer to an Ety like experience, quite possibly due to the 8 ohm impedance.  However with non-bass heavy music the RoCoo gives a 3D presentation that is a good step up from the 4S and Clip+.  Imaging is very good and spatial ambiance recreation quite nice.  If you want deep, powerful bass look elsewhere, but if your music collection consists of acoustic and/or vocal based music, the ROCOO Power is a great pickup.  The score reflects the bass issue.  3/10

801 (with GAME card):  With better deep bass control than any of the above sources and great imaging, the 801 sounds very good with the K3003.  The spatial recreation isn’t presented quite as naturally as with the RoCoo Power, but detail levels are superior as is the overall presentation and placement within and size of the soundstage are excellent.  8/10


Portable Sources, DAPs with Amps

iPhone 4S with i.Fuzen:  The presentation isn’t that much different between the HPO and the i.Fuzen, although the i.Fuzen is brighter.  Unlike with most headphones I have tested with the i.Fuzen, the K3003 soundstage size really doesn’t change (open up and become more laid back) between the HPO and amp out.  What did change quite a bit was the bass region as the i.Fuzen controls the region much better, adding depth and improving texturing.  While A/Bing I was surprised by the large difference in the bass notes as they almost sounded like they were from a different song when going back and forth.  The i.Fuzen also cleans up the rest of the presentation, smoothing out the sound without losing any detail. The sound isn’t as liquid and the soundstage isn’t as focused, clear, and concise as that of the much more expensive 801.  6/10


iPhone 4S ->

Pico Slim: When paired with the iPhone 4S, the K3003 has soundstage clarity and precision of the 801, but with a leaner and lighter sound.  Bass, while not lacking, is a bit on the lower side of the amp spectrum, although it does seem like the resolution of the iPhone is holding the sound back a bit as the Pico Slim with the modded iPod is much more spacious and involving.  6.5/10

Stepdance & uHA-120: Similar to the comparison with the modded iPod, but the presentation is rougher and not as refined due to the iPhone. 6.5/10

Cruise: The Cruise really brings out the best of the K3003 in this configuration with deep, controlled bass, an exciting, fast, and articulated sound wrapped in a larger soundstage than the Stepdance, uHA-120, or Pico Slim.  Compared with the Portaphile, the performance is close with the Portaphile delivering a more effortless low end but the Cruise offering a more punchy and 3D presentation with only an ever so slightly smaller space.  There is a slight hiss with the Cruise.  7/10

Portaphile 627: The iPhone is the weak link in the chain as the Portaphile isn’t a large step up from the Pico Slim, although the tonal qualities are different and the Portaphile still is superior.  7/10


Modded iPod ->

Pico Slim: Unfortunately, compared with the Portaphile the PS is an underperformer.  Comparing with the 801, the sound is brighter and leaner, but the overall quality is similar, except in the bass depth and detail levels where the 801 wins.  7/10

Stepdance: While the Stepdance sounds good with the K3003, it isn’t a match for the Portaphile.  It technically is superior to the Pico Slim, offering more bass control and oomph with a more neutral sound vs. the brighter sound of the PS, although detail levels seem a hair lower.  7.5/10

uHA-120: The 120 isn’t much different than the Stepdance, except it has a bit brighter sound and a light bit better transparency with the K3003 to go along with a slightly more laid back, wider presentation.  The bass of the Stepdance is slightly more extended and controlled.  If I had to choose between the two for the K3003 I would pick the 120, but it is very close.  7.5/10

Cruise: Very nice sounding combination that is a step above the other amps except the Portaphile, as the Portaphile delivers a bit more detail and the recreation of space is more open.  The combination is dynamic and spacious with very good bass reproduction.  There is a slight hiss that is audible between tracks, reducing the score 0.5.  8/10

Portaphile 627: I couldn’t believe my ears when I heard this combination.  It was oh so spacious and lush sounding, but with plenty of detail, making the Pico Slim sound small and uninvolving.  In comparison with the other amps, it offers a better, more realistic sense of air within the soundstage, which is larger than the other amps.  Bass is well controlled, punchy and deep.  Treble is extremely smooth and the amp controls the K3003 so well the weaknesses it has are less noticeable.  10/10

EPH-O2: Spacious sound with powerful bass and an overall good, controlled presentation.  Compared with the Portaphile, the O2 is a bit more spacious and laid back but with less depth to the soundstage and not as good of imaging, creating a slightly flatter and less involving sound in comparison.  Compared with the Cruise, the sound is more laid back with a bit better bass texture and no hiss.  Dynamics are slightly lower than the Cruise and the presentation doesn’t have quite as natural of an overall presentation, if just by a bit.  8/10


Desktop Sources

Cruise: As a DAC, the Cruise performs quite well with the K3003 offering a dynamic performance.  Detail levels are quite good and with the Reference port, there is a very good, natural sound.  Unfortunately, there is a low level of hiss, but it is not there when music is playing.  The difference between the D1 and Cruise spatially are marginally different with the D1 having a slightly better sense of overall depth and air within the presentation.  8.5/10

D1: The D1 doesn’t sound too much different than the Cruise, but the details are articulated and separated a bit better, and there is a bit more bass quantity. Surprisingly the modded iPod -> Portaphile combo has a bit more space and air that sounds more natural, although the refinement is a slight hair below and the detail levels are not quite as good with the iPod/Portaphile. The score is reflective of the immersive presentation of the iPod/Portaphile.  9.5/10


Source Summary: AKG did a good job making the K3003 easy to drive and work well with lower end sources such as the Clip+ and iPhone, although it does scale nicely with higher end sources.  If you go light and just use an iPhone, you won’t be getting the most out of your K3003, but the sound will still be superior to any other universal IEM I have heard.




K3003 vs. Custom IEMs

So, can the K3003 replace custom IEMs?  It depends on what you are looking for.  It is the best sounding universal IEM I have heard to date, but still falls short ultimately of the sonic performance, comfort, and isolation of custom IEMs.  For those that don’t want to take the plunge into custom IEMs and risk getting a sound signature you don’t like, the K3003 is excellent as it allows you to change the sound signature quite a bit and if you don’t already have high end custom IEMs, you should be very satisfied with the sound.  Depending on your needs/wnats and as long as you know what to expect and the K3003 could be a great buy in place of custom IEMs.



The K3003 is a fantastic universal IEM that offers quite a bit for the extremely high price, from 3 different sound signatures to a stylish yet durable build, but not skimping on the sound.  I haven’t heard a better sounding universal, and while the sound is in the same league as many top-tier customs, it didn’t make the all-star team.   What the K3003 does offer, in addition to beauty and a rock solid build is excellent clarity to go with great transparency and imaging as well as a very capable yet not overpowering low end.  In fact, the K3003 excels at just about everything from a technical performance standpoint.  The natural tone of the Reference Port was a very pleasant and the ports allow you to focus more on the bass or treble regions if you want.  When compared with similarly priced custom IEMs, a frequency coherence issue becomes apparent in the region where the dynamic driver and balanced armature drivers crossover, which is most evident with the Reference Sound port.  And while the presentation does offer good space, it is not quite as spacious as a custom IEM.


The shape and fit weren’t ideal for me and I couldn’t get a proper seal and comfort at the same time with the stock tips, but people with smaller ears shouldn’t have an issue.  As with any universal, getting a good seal is important, so for the price, the K3003 could have used some additional ear tip types to fit a wider range of ears; not something you want to be concerned with after you drop this much on earphones.  However, once you do get a good fit you are in for a fantastic performance that is well balanced and can handle any genre you throw its way, the K3003 will deliver.



–       Amazing sound from a universal IEM that is full, detailed, and articulate

–       Excellent clarity, great transparency

–       Powerful, refined, and balanced bass presentation



–       Shape and stock ear tips didn’t fit my ears well and caused discomfort

–       Coherence issues between the bass and midrange drivers

–       Treble is peaky with the Reference Sound port





Having a life-long love of high-quality audio and gadgets, average_joe got back in touch with his audiophile side after a hiatus caused by life. His focus became headphones and related gear as the size and price fit his life better than home audio. He believes the entire audio chain is important, and likes to continue to think past the headphone and on into the head, as he believes understanding the details of how we hear will lead to a better audio experience.


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