WATCH FULL REVIEW HERE: 

PROS:

• Follows the JM-1 Target
• Very well-balanced and versatile on different genres
• Safe and inoffensive tuning
• Rich and warm tone
• Superb extension on both ends
• Good coherency with minimal metallic timbre
• Good fit and accessories

CONS:

• Might be too safe for some
• Not the most technical sounding IEM for the price
• Bass can sound too smooth
• Can sound too warm
• Treble energy can be lacking

WHO THIS SET IS FOR:

• Measurebators 
• People who like a safe and versatile tuning
• People who want good and stable fit
• People who like a coherent and consistent sound

WHO THIS SET ISN’T FOR:

• People who want a fun and engaging set
• People who want a tactile and nuanced low end
• People who want an open sounding midrange
• People who want a dynamic listening experience

RECOMMENDED GENRES:

• All genres minus mezzo-soprano female vocals

SHORT REVIEW:

Meta means optimal, and the KE4 is probably the most optimal sounding IEM. Superb tonal balance, phenomenal end to end extension and a tuning that will sound great with most genres. However, it’s biggest strength is also its biggest weakness as it lacks the excitement that I usually get from more V-Shaped sounding sets. Regardless, the KE4 and the JM-1 to an extent proves that audio has not stagnated quite yet. RECOMMENDED!

FULL REVIEW

Meta. Mainly used in video games, now being used for headphones? What’s happening? Well, to tell a long story short that I will also tell again later in this review, the recent advancement of headphone measurements lead to the creation of update preference targets and compensation that brought about the most “scientific” way to tune headphones today. 

But this only fuels the flames for the war between the “trust your ears” clan and “measurebator” clan to further discuss what it is exactly is the best way to evaluate headphones. So let me give my two cents, along with a comprehensive review of one of the better IEMs to follow the infamous JM-1 target.

DISCLAIMER: The KE4 was sent in exchange for my honest thoughts. I was not paid or compensated to say anything about the product.

ONE TIME FOR THE MEASUREBATORS, ONE TIME FOR THE FR BROS

Normally, I talk about the history of the brand in this section. However, I want to add a bit of context to that entire intro discussion on “preference bounds” . First, let’s talk about Kiwi Ears.

This is my second rodeo with Kiwi Ears, which is also my second rodeo for their isobaric 2DD tech that they seem to enjoy doing. My first experience with them, the Kiwi Ears Quartet was less than desirable. I enjoyed how it looked, I enjoyed how it fit, I did not enjoy how it sounded. Tonal issues, coherency issues and QC issues plagued that set that lead me to give it a rather lukewarm review. I didn’t think it was unbearably bad, but it could have been better.

Well, Kiwi Ears may have just made something better with the KE4. Same isobaric configuration but a hell lot better coherency. But arguably its selling point is that it follows the infamous JM-1 target (specifically the 10db tilt version). But what the hell is the JM-1, what are preference bounds? What even are all these fancy terms? Well, let me give you a very brief explanation to all of this. 

Before I continue, I would like to preface this by saying that I will be talking about some rather nerdy crap and you can completely skip this entire part if you’re not interested. However, I highly recommend you read this as it provides good context of my conclusion on the KE4 later. 

Also, I will be linking a couple of articles and videos to thoroughly explain the many topics I will cover in this review as I oversimplified a lot of information for the sake of time and sanity. Check it out at the very bottom if you’re interested.

Gentlemen, A Short View Back To The Past

The evolution of audio products have been a slow, steady but progressive path from speakers to headphones. However, headphones in particular have only had a couple of decades of thorough research done and even shorter for in-ears. Heck, the first few “good” in-ears only appeared in the later part of the 20th century and many of you have probably been born longer than the development of in-ears. 

This means that the technology to properly evaluate audio gears such as headphones (I will put headphones and in-ear in the same category for redundancy’s sake) have been less than ideal. Free-field was the generally accepted measurement standard back in the day, but this proved to be problematic by a couple of people. This lead to the creation of the Diffuse Field Head Related Transfer (also known as the DF HRTF)

To explain an EXTREMELY complex term, the DF HRTF was not made as a preference target like the many targets you might find on squig.link, but is made to calibrate the measuring rig to be as accurate as possible. I HIGHLY encourage you to read up on the articles and documents explaining these concepts if you want to have a better understanding and appreciation for why headphones sound the way that they do now. 

Despite the DF HRTF being basically the most accurate way to calibrate a microphone to measure as accurately as it could, the desire for a point of reference that is actually listenable was yearned for. Harman lead this development with their famous research that has now become an adjective to describe headphones. You’ll probably see a lot of reviewers and casual people call something “Harman-ish” to describe headphones and that’s for a good reason. 

The measurement standard that we have been using has been based on the Harman research and 711 (which are based on the IEC60318-4 standard). While this has been the tried and tested standard for a good couple of decades now, companies like B&K have been developing more accurate simulations of the head and torso with the likes of the B&K 5128-C. 

A lot of funny words and terms here, but all you need to know is that measurements are evolving and so the standards need to change. 

With this change, a new way of evaluating headphones also needs to evolve. This is where the good people at Headphones.com come into play as they have been hard at work developing a pretty solid way to evaluate headphones. With the use of the Harman research and their funky B&K 5128, they’ve developed a “preference bound” that is scientifically, objectively and statistically the most “accurate” measurements that is available right now. 

In-ear monitors specifically, the evolution has moved towards the JM-1. The meta tuning. This is based on the same DF HRTF used on headphones, but removing the influence of the parts of the ears that aren’t being affected by in-ears (aka that big flappy thing on the side of your heads) and compensated to the average ear. 

I’m not gonna explain how the JM-1 target works or why it’s currently the most accurate target to follow the preference bound as I feel like I’m not the right person to talk about it (hint hint, links at the bottom). But the JM-1 is the closest we have to objective evaluation of neutral tuning for in-ears. 

So in short, headphone measurements not good. People do research to find best way to measure headphone, people make headphone target as preference bounds, JM-1 exist for in-ears. That’s the scientific and research side of audio and they aim to make audio evaluation more accurate. 

Why Do You Even Need Accurate Evaluation?

If you’re on the clan against frequency response graphs, you might be wondering why you need this if you can just find headphones that sound good to you and know absolutely nothing about how it measures. Well, measurements exist so that we have a general understanding of what is “good”. Good is subjective, but how we can get good can be measured. That’s what the research is for in the first place and even your favorite headphones exist thanks to the evolution of objective evaluation for all audio equipment over the years. 

Now that I’ve talked in depth about the whole measurement rabbit hole, let’s talk about the KE4 on its own. 

UNBOXING

To make a rather simple unboxing short, the Kiwi Ears KE4 features the usual Kiwi Ears illustration (some of the best in the market) with basic information in the back.

Here’s a full list of the accessories:

• KE4 IEMs
• 4 Core Cable
• 3 pairs of Kiwi Ears Flex Eartips
• Replacement Filters
• Carrying Case

I’m slightly disappointed with the unboxing experience of the KE4, fundamentally because of how spartan it is. While you do get Kiwi Ears Flex eartips along with a nice case, this is not a $200 unboxing experience. You ONLY get the flex eartips and the case is the same one that comes with their budget IEMs. 

BUILD & FIT

The build and fit situation of the KE4 is near identical to all their previous resin-based in-ears in terms of both the quality and the comfort. Least to say, this is probably the best large fitting in-ear that I’ve ever worn. 

But let’s tackle the elephant in the room first: isobaric 2DD + 2BA hybrid with a 3-way passive crossover and 3 independent sound tubes. Once again, Kiwi Ears attempts the isobaric configuration, and this time I’d argue they succeeded. 

Before I continue, I want to address that this is Kiwi Ears’ first non-music related naming. I may be incorrect and that KE4 is actually a musical notation for something (or Kiwi Ears have released a product that doesn’t have musical references) but to my knowledge, this is their first. 

Externally, the aesthetics resemble the Kiwi Ears Quintet with the dark inner shell and silver faceplate. Contrary to what many people have said about the Quintet’s “boring” look, I’d argue that a silver faceplate like the one in the KE4 looks very clean and handsome. I’m not going to give it the award for the best looking IEM, but it’s simple and looks good in and out of the ear. 

But arguably the issue that most people will have with the KE4 is its size. This thing is an absolute chonker and people will smaller ears will not have a great time. However, the shape is akin to their cheaper sets like the Quartet which means this thing fits in my ear like a glove. Not as well as the smaller Quartet, but certainly well enough to keep me from complaining about the fit. 

The problem I had with it was the long term comfort will vary depending how you fit it in your ear. If you have the wings digging into your ear in an uncomfortable angle, it will hurt after a couple of hours. However, this can often be remedied by adjusting it before hand. 

Another issue I had was the driver flex. No air pressure build up is always nice, but the driver flex may be a bit uncomfortable during first wear. I didn’t really experience any long term problems because of this, but this is something to note if you’re sensitive to the crinkling of the driver. 

As for the cable, this is a very aesthetically pleasing and comfortable cable with very premium interface. I want to say this is one of, if not, my favorite 4 core cable on the thinner side, but more companies have been providing really good quality cables that I can comfortably say that the KE4’s stock cable can live amongst the greats. Maybe a modular termination would’ve made this even better, but I don’t think it needs modularity with how easy it is to drive (more on that later). 

SOUND

Sound Signature

Here we go, the sound signature of the KE4 is what people would call nowadays, “Meta”. But what does that mean? In short, it falls within the preference bound that I mentioned early in the review based on the B&K 5128 DF HRTF and the JM-1 compensation HRTF. What this means is that it has a well balanced, well-extended and consistent sound that is made for all-rounded listening sessions. The KE4’s nuanced characteristic is its low end focus, particularly in the lower mids with a slight hump that you can hear when listening to tracks with a prominent lower to mid vocal presentation. Timbre consistency is surprisingly good, considering their last isobaric hybrid was admittedly a mess in terms of coherency. But let’s get deeper into that in a bit

Source Pairing

The KE4 is arguably one of the most versatile sets when pairing with whatever source I plug it into. From my cheap dongles to my all-powerful SK02, the KE4 ranges from sounding good to sound great. It’s also very easy to drive as I never had any problems with volume at all, but a more powerful or cleaner source will net you better sound (duh)

Volume Levels

I was personally expecting the KE4 to be a volume scaling  monster, but that lower midrange emphasis feels so out of place the higher the volume is and forces me to go mid listening volume to keep tonal integrity and an enjoyable listening experience. It could also be attributed to the rather late eargain, but I’d argue that also plays a part with the lower midrange preventing me from going higher

Bass

The KE4’s bass is what you might expect a “meta” bass sounds like. Clean, subbass oriented with good extension, rumble and kick without much bleed into the mids. This theoretically makes it a very ideal level of bass for whatever songs you’re listening to and to a point, I would whole heartedly agree. However, the problem with is is the smoother than tactile midbass presentation that ends up making the bass sound more linear than dynamic. It’s not the worst I’ve heard, far from it. I’d argue that the KE4 is one of the best to balance that subbass and midbass tuning. But whether it’d be the isobaric configuration just not giving enough nuance or the quality of the driver just lacking in refinement, the KE4 is closer to having a “slow” presentation than a snappy one to my ears. It’s not that slow to make it incoherent with the speed of the rest of the frequency, but it certainly affects it. 

Mids

This is the region where I’m most divisive on the KE4. While I am aware and can appreciate the “neutralness” of the midrange, I also find that the combination of a boosted lower midrange and toned down upper midrange with a late eargain makes this a very relaxed and not very engaging listening experience. On a positive not, male vocals, electric guitars and instruments that want a lot of lower midrange energy sounds perfect on this. A specific example would be the song Blue by Amateurish. Most IEMs present the overall sound in a rather thin and pale manner that sounds lifeless. The KE4 is able to give the song much needed body and lower midrange while keeping the overall tonal presentation relatively uncolored. However, the problem rises when you throw this into tracks with thicker female vocals that get drowned out by the lower midrange. Take for instance Laufey and Samara Joy. I did NOT have a satisfying listening experience with either of them on the KE4 whereas other sets, particularly leaner ones, do. 

This is where the conversation of the “meta” tuning comes into play, to which I’d defend this kind of tuning for being one of the few kinds of tuning that can provide good note weight without total coloration. The aforementioned song Blue is the best example for this and older pop tracks like Earth, Wind & Fire, Fleetwood Mac and even the Japanese fusion band Casiopea sounds great on the KE4. The problem rises when you throw in vibrant upper midrange focused tracks that also have lower midrange emphasis and you start to hear why the KE4 wasn’t my cup of tea at the start. My usual test tracks included Laufey and Samara Joy and they did not sound great. But throwing this into older tracks and now we’re talking. 

Treble

Similar to the bass presentation, the treble is arguably the best thing about the KE4 in terms of neutrality. To my ears, the KE4 follows such a beautiful glide from the lower treble to the upper treble with a fatigue free but nuanced treble presentation. I honestly don’t mind that it’s not as bright or vibrant as my usual preferences as a bit of relaxation is in order if I want to keep my hearing, but the KE4 stands out by having such a refined and consistent sounding treble that I don’t usually find in hybrids, let alone an isobaric hybrid IEM from Kiwi Ears. The extension and air is fantastic, the details are present but not overbearing and the overall energy level is just right. Obviously I’d want more, especially considering that the treble sounds the way it does mainly because of how thick the low end is, but I don’t mind the treble if the lower mids sounded a little bit thinner and the bass more midbass focused than subbass focused. 

Technicalities

Technically speaking, the KE4 sits right around what you might expect from the $200 mark. Good separation, superb dynamic and transients, solid resolving ability and good headstage. But arguably the best thing about the KE4 is coherency. Considering that this is Kiwi Ears second (correct me if I’m wrong) isobaric DD + BA hybrid, the KE4 is a home run in terms of tonal coherency. I did not feel like the bass lagged behind the mids or the treble, albeit there is still a little bit of a metallic tone in some songs. Dynamics and transients are decent, although definitely not the best that I’ve heard. Overall, good technical chops for the price but nothing too fantastic. 

COMPARISONS

vs Kiwi Ears Quartet

I first want to compare the KE4 to its isobaric predecessor at half the price, the Quartet. I was not very impressed with the coherency and driver quality of the Quartet and thought that if it didn’t have that annoying metallic timbre up top, it would honestly be a pretty solid v-shaped set that sets itself apart by being as smooth as it is. The KE4 is a complete contrast with refinement being the name of the game and arguably dynamic and transient response. Raw tuning, I find the Quartet more fun and engaging. But that;s by design. The KE4 is neutral warm with a slight airiness while the Quartet is pure V-Shaped with big bass, scooped mids and big treble (spike). In short, the KE4 is not necessarily an upgrade to the vibrant and chaotic Quartet, but instead a more neutral-warm option that also features that isobaric DD hybrid configuration that Kiwi Ears flexed in the Quartet

vs Dunu Davinci

Arguably the closest relative to the KE4 in configuration and tuning Philosophy, the Da Vinci is the KE4’s warmer, bassier and more fun cousin with a more engaging, punchier and deeper presentation that I personally preferred over the KE4. However, the KE4 is admittedly the more “balanced” option out of the two due to the rather big bass boost of the Da Vinci over the KE4. Coherency is similar on the two but the Da Vinci is certainly the more fun option to listen to between the two. The KE4 is you in the office and the Da Vinci is you on the beach. Same, well-rounded tuning with one of them letting loose and being a little bit more fun. 

vs Simgot Supermix 4

From isobaric to quadratic, the Supermix 4 imbues the previous tuning standard of the Harman 2019 compared to the JM-1 infused KE4. Flairs out of the way, the Supermix 4 is distinctly thinner and more vocal forward than the KE4 which is warmer and more relaxed. You could almost say they’re the exact opposite in terms of tonal balance, but the Supermix 4 is toned down from the usual Simgot tuning. Technically, the Supermix 4 has a cleaner sound out of the bat but the KE4 has a more consistent tone throughout the sound thanks to its flatter presentation. I’d say that both sets aren’t really my cup of tea (Supermix 4 having poor bass dynamics and KE4 having too much lower mids) but both sets occupy the opposite sides of the same nerdy coin. 

vs Yanyin Canon II

My favorite midrange fun hybrid still reigns supreme on what I find to be the ideal tuning for in-ears. While the KE4 offers a more relaxed and “neutral” tone, the Canon II offers a more engaging, more open and more detailed listening experience that would make perfect sense considering this is almost twice this price of the KE4. Giving the KE4 the benefit of the doubt, it is a generally smoother listening experienced compared to the Canon II. The Canon II suffers from a bit of a distinctly metallic and rougher treble presentation that both aids and affects its tonal presentation to not be the most neutral. But then again, that’s not why the  Canon II exists in the first place and provides a more fun listening experience compared to the KE4’s more relaxed tone. 

CONCLUSION

Now, it all boils down to the burning questions. Does an IEM tuned to JM-1 sound good and what does this new HRTF spell for the future of in-ear monitors?

Let’s first talk about the KE4. Theoretically, the KE4 is the “safest” IEM to get under $200. The combination of a consistent tonal balance with good extensions on both ends, rich midrange, good details and technical ability. There’s technically nothing major to fault about the KE4 in a technical point of view. However, my preferences lie outside what the KE4 delivers. First, I like my midbass thick and meaty with the mids slightly scooped. The KE4 is the exact opposite with a very clean low end presentation and a borderline thick midrange presentation. Pair that with the upper midrange that lacks energy to my ears and sounds occasionally drowned in the lower midrange and you get a set that I’d only be picking up when I want to listen to retro pop and rock tracks that NEED that body. Not necessarily my “all-rounder” listening choice. 

But that’s the thing about the KE4. Despite my personal comments on it, I still believe that this is an IEM that most people would probably thoroughly enjoy. Not only from my personal experience with talking to people and their preferences, but also the data gathered to create the JM-1 that the KE4 uses as a point of reference. Obviously, I don’t know if they actually did use the JM-1. But with how closely it follows the said tuning, you can’t deny that they are at least aware of what direction IEM tuning will go from this day onwards. 

I believe that the JM-1 and to an extent, the KE4 is the right step to the evolution of IEM tuning. It may not be to my preference, but it’s certainly better than what we had before. This is less offensive and more balanced than the standard we’ve set for ourselves prior. 

However, I also think it’s important that we understand that the JM1 is not a preference target to follow 1:1, but a preference boundary that we can modify depending on our own preferences. I may not like the JM1, but I know I like the Simgot EA500’s tuning and I can look at the frequency response graph to understand where the EA500 lands within the preference bounds. And the same can be said for every single IEM to come in the future that will use the JM1 as a point of reference to create their ideal IEM. 

Thank you for reading my review on the Kiwi Ears KE4. If you would like to order one, consider using the non-affiliated link below: https://www.linsoul.com/products/kiwi-ears-ke4

RESOURCES: 

Diffuse Field: https://headphones.com/blogs/features/diffuse-field

Understanding Headphones.com IEM measurements: https://forum.headphones.com/t/understanding-the-headphones-com-iem-measurements/23607

On the Standardization of the Frequency Response

of High-Quality Studio Headphones: https://hauptmikrofon.de/theile/1986-3_Standardization-of-studio-headphones_JAES-1986.pdfThe New IEM Meta Explained: https://www.youtube.com/watch?v=EZoKPtzjdtQ