This earphone is a 'world first'... yet I feel like I’ve heard it before

Another month, another breakthrough in the IEM world. Today it's Kiwi Ears and their new Halcyon earphone, and its use of a MEMS (Micro-Electro-Mechanical Systems) driver. It's been marketed as the 'World’s First MEMS+1DD+3BA Tribrid IEM', and who can argue with that?! Well, Binary Acoustics probably... But enough with the politics, we're here for the sound (more on that in the Competition section below).

• Get the Kiwi Ears Halcyon for $250 $209 at Kickstarter

And for around $250, the Halcyon offers an enjoyable enough, coloured, and not at all neutral, sound profile. It's not perfect, but what it does well, it does incredibly well. And even though at its discounted $209 early bird Kickstarter price it won't be making my best budget IEM list, it'd be a contender for a mid-priced IEM guide.

Let's dig into its sound profile, the pretty impressive competition, and notes on the build and comfort...

Sound profile

Overall, the Kiwi Ears Halcyon is a bassy boy with an elevated upper midrange, and a specific splash of treble that reframes a well-measured lower midrange as a little lean. Hip hop, jazz and classical sound great on this IEM, and although vocal-heavy tracks are clear, they can start to grate ever so slightly.

There is plenty to like about this Kickstarter-priced $209 IEM: it sounds detailed, has a great transient response, and that bass!!... but at its full $259 price, it's not the only MEMS IEM in town.

Bass: You certainly get a lot of it, but it’s not a bloated barrage. On Mac DeMarco’s Heart to Heart, his bouncing electric bass guitar is full of texture and detail. While on tracks like Sade’s No Ordinary Love or Erykah Badu's Other Side of the Game – which put both sub- and mid-bass up front in the mix, it's weighty and powerful. I'm sure there's more detailed bass out there, but the Halcyon avoids feeling lazy and fluffy. Of course, an elevation around 8kHz works as a nice counterpoint. Did someone say 'V-Shape'?!

Halcyon’s bass reminds me of the Kiwi Ears KE4, but its sub-bass plays a bigger role, thanks to a steeper slope into the midrange, which dips down deeper than the KE4. Speaking of the midrange…

Midrange: This is where people will either have an issue with the Halcyon, or find their favoured sound colourations. For me it’s the former. Its frequency response definitely aligns more with the Harman than JM-1 IEM target, but actually, it ends up being caught somewhere in between. On a graph, the lower midrange perfectly hugs the Harman target. But due to a whopping elevation between 1kHz and 2.5kHz, that lower midrange sounds a little weak.

What does all that mean? For me that means most instruments and vocals lack a bit of body, yet on certain tracks can shout too loudly for my attention. Before I Saw the Sea by Me and My Friends highlights the pros and cons of Halcyon’s mids. The main female vocal is clear and forward; there’s plenty of clarity and detail to the backing male and female vocals; but the clarinet gets properly reedy, and though I wouldn’t call it screechy, there are moments where it’s not far off.

In quieter songs and ballads, whispering vocals can feel close and sound pretty great. And when it works, as with the harmonies on Crosby Stills and Nash's You Don’t Have to Cry, things seem far better balanced. But it's a little hit and miss.

Treble: According to the Squiglink charts, there’s a prominent elevation at 8kHz, and even though this is a common spot for an "artifact of the measurement process", according to the site, after messing around with EQ I definitely hear it. Combined with that elevated upper midrange, this makes everything seem a little brittle. Of course, if you get the right song, it can mean more micro-details in rhythm guitars, mouth clicks and the like. But I found by taking 1.5kHz and 8kHz down a few dB, it took the edge off and helped the Halcyon's tone sound more realistic, without making it any less impactful.

That may seem like nitpicking. And it is. I can totally imagine some listeners enjoying the Halcyon's sound as it is. And I might have as well, if I hadn't just reviewed another MEMS-driver IEM at around the same price point...

Competition & value

Competition: I'll be frank – I think most of my issues with the Halcyon come from comparing it to the Binary Acoustics EP321.

We're spoilt when it comes to IEMs today and although Kiwi Ears has made a big thing of its use of a MEMS driver in the Halcyon, they weren't the first. At the tail-end of 2025 Binary Acoustics' EP321 showcased the MEMS technology and a wonderfully detailed and rich sound too. And it takes the wind out of Halcyon's sails.

EP321 has more detail than the Halcyon, and yet its upper midrange and treble doesn't grate on me at all. It's all a balancing act, and the EP321 has a holistic frequency response that doesn't leave me with any niggles. At the same volume, the EP321 seems more poised, fuller, less shouty and yet achieves it with an ever-so-slightly clearer sound profile.

I think it's because you get less sub bass with the EP321, a slightly fuller mid-bass and lower midrange, less forward (shouty) upper mids and then a more 3D treble, with airy notes to better sculpt the sound, which the Halcyon lacks.

But wait, the EP321 retails at $310. This isn't a fair fight, I hear you cry!

Well, a few months is a long time in IEM World, and you can now buy the Binary EP321 regularly for $279 over at Amazon. When you factor in that the Halcyon is only $209 for early bird Kickstarter backers, and will then be $259 at retail, there's only $20 in it.

Elsewhere, you've got the aforementioned Kiwi Ears KE4. Now, this is a New Meta-with-a-bass-boost IEM, so it's not going for the same pre-New Meta sound profile of the Halcyon. But it's worth bringing up for a couple of reasons.

First, it has comparable sub- and mid-bass. However, I think the KE4 does a 'better' job with the lower midrange. That is, the bass bleeds a little into them, and makes everything a little more meatier. For me, the KE4's midrange is just flat out better than the Halcyon's – more balance means better tonality, and instead of shouty upper mids, things get relaxed, only to get a shot in the arm with a well-extended treble. It's not perfect, of course, but it's only $199, and if you can forgive its utterly shit cable, it's definitely a less exciting, more balanced alternative to the Halcyon.

Build & comfort

The Halcyon has got me confused when it comes to build and comfort. It feels light and flimsy in hand, and yet its fully metal shells look and feel like good quality. Yet, I can't shake that there’s something that feels cheap about their weight and reduced size. Even comparing them to my $50 Kiwi Ears Cadenza II, which is bigger and ever so slightly weightier, and I prefer the feel and the fit of the cheaper set.

Feel plays a role in my enjoyment of IEMs (and headphones), so I think it's worth stressing the point – the Halcyon ear pieces feel cheap to me. And due to their stylised shape opposed to the usual contoured design, they protrude considerably from my ears which, although not uncomfortable, feels awkward.

One thing I love is the cable. It's a really well-built, beautifully brown (never thought I'd say that!) cable that isn't memory prone, isn't too tacky, and is generally great to use.

Should you buy it?

If the Kiwi Ears Halcyon was to remain at the early bird Kickstarter price of $209, and I had never heard the Binary Acoustics EP321, it's an easy recommendation to anyone that wants a detail-rich IEM with an incredibly fun bass response.

But at $259, with the fierce competition out there, things get more complicated. You have to consider that for an allrounder, V-shape sound profile the Halcyon is actually quite genre-specific. If you like vocal-heavy music, you might really respond well to the Halcyon's elevated upper midrange. I found it was great with some tracks, but overstepped into shouty territory at times. The bass is great, but the lower mids lack body.

Personally I would either head over to the Halcyon kickstarter right now and buy it for $209, or I would wait a few months and pick it up around Black Friday for around that price. At $259, I'd consider the $20 more expensive Binary EP321, or the $59 cheaper Kiwi Ears KE4.