InEar ProMission X Review: A Galaxy of Sound

This is my first time listening to an InEar IEM. And I have to say, if all of their IEMs sound as good as the ProMission X, I’ll be a fan for life. I’ve listened to a lot of high-performance buds over the years. And as skilled as all these IEMs may be, many of them all blend into one hazy memory. I’m also not especially generous with my compliments. But get ready for me to drool over the soundstage of these things. What makes the ProMission X stand out from the crowd? Sorry for the spoiler. But let’s take a closer look in this InEar ProMission X Review.

InEar ProMission X Review

IN the BOX

ProMission X IEMS with 3.5mm braided cable

4 pairs of silicone ear tips (sizes XS, S, M and L)

3 pairs of Comply TS400 foam tips (sizes S, M and L)

Gold-plated 1/4‘‘ adapter

3 cleaning cloths

InEar hard leather case

Tool for changing sound settings

Earwax filter set H3

Drying cap

Contents inside ProMission X Packaging


No problems here. Great sound isolation on these buds. The stems are quite short, so the eartips sit very close to the shell. And though the shells look like they have a lot of weird contours, I found the fit very snug and comfortable. The shells are also very light, so you’ll probably forget you’re wearing them.

InEar ProMission X IEMs with 2-pin cable

ProMission X Shell contours


The ProMission X sports 10 balanced armature drivers with a 4-way crossover. And although the shells of ProMission X are aesthetically gorgeous, the packaging is unassuming. The IEMs come in a simple round leather container. No drawers or compartments like you find in the latest Empire Ears models, for example. And the box it comes in doesn’t look like anything snazzy. (Now, don’t quote me, that’s the package they sent to us. And in the user manual, there’s a picture of a different hard-shell case).

The 3.5mm 2-pin cable doesn’t look like anything special either, and there’s little information on InEar’s website to go on. But again, the shells are a work of art. InEars used a hybrid material that combines jet-black violet wood combined with “acrylic in shimmering mother-of-pearl sky-blue” to “establish an optical analogy of the universe.” And given the sound signature, the analogy couldn’t be any more fitting. But more about that below in the soundstage section.

ProMission X Shell shape and size

The ProMission X is easy to drive, and even your mobile device will be enough to power it. But for the purposes of this review, I used the FiiO Q5S.



A satiating level of bass presence here, and certainly enough oomph to do full justice to pop tracks. Listening to rock, you can expect warmth and richness. But it avoids becoming hedonistically lush. And while the sub-bass frequencies are there, it’s far from boomy. Listening to classical strings in this range, you’ll hear some nice texture, but don’t anticipate a particularly raw or dry sound. But the timbre and tonality has tons of substance, all combining to create a majestic and somewhat fluid feel.


The resolution on these things is particularly impressive. The ProMission X is just so pure and absolute in its presentation. Nothing about it feels contrived. At the same time, it avoids sounding sterile, though some audiophiles may hunger for more “balance pizzazz”. In fact, it feels big and bold, and the soundstage plays a large role. But more about this below. Although you’ll hear some low-mid presence, the upper midrange is slightly highlighted. So, while tracks have body, vocals (especially female vocals) shine through the mix a little. But there are no wacky bumps, so it’s very tastefully balanced in this range. The response is also fairly speedy. And combined with the midrange balance, tight, higher pitched snare hits become very dynamic and hard hitting, breathing plenty of life into rock and pop-rock tracks.

With respect to separation, I’ll admit that I’ve probably heard better at this price point, specifically in the lower mids. Guitar strums in that range, for instance, could use a little more definition. (Nick Drake’s Pink Moon is an example). But let’s remember that these IEMs have a a somewhat warm sound signature. And the ProMission X has so many great defining qualities, that I’m just nitpicking at this point.


Again, listening to the highs, it’s clear that In Ear has hit the perfect balance with these buds. Plenty of snap and crispness when listening to percussion in this range, but it avoids reaching a fatiguing level. And in general, this is an easy headphone to listen to for long stretches. Also, female vocals are super sweet up here. Not particularly weighty or velvety. Rather, vocal performances are quite smooth and airy, again, with top-notch transparency. 


The soundstage is up there with one of the best (or most interesting) I’ve ever heard. In fact I’d love to test it back to back with a 64 Audio model. Not only is the space incredibly vast, but the sense of dimension is miraculous. You know when you go for a massage and the masseuse reaches muscles you never knew you had? (Not the muscle you’re thinking). Well, this is how it feels listening to the Pro Mission X. With respect all three dimensions – depth and width and height – there are so many clear gradations along all of these axes, that to call it holographic would be an understatement. And it’s probably the closest I’ll ever to get to experiencing synesthesia. Of course, the psilocybin probably helped. But again, midrange vocals are so perfectly placed within the mix that, despite its grandness, you feel a very intimate connection with the sound. It’s an utterly immersive experience.


Pros: Whopping, immersive soundstage; terrific resolution; beautifully balanced.

Cons: Less than miraculously tidy (but you can’t fault it, given the warmer profile); balance may not be unique enough for audiophiles who own everything.


Elegantly balanced, yes. (Though more eccentric audiophiles may find it boring). But every memorable IEM has at least one unique quality. And I’m guessing that the expansive, stunningly multidimensional soundstage, along with the fantastic resolution are the two lasting impressions you’ll be left with after listening to the ProMission X. And overall, it’s one of the classiest and most enjoyable IEMs I’ve tested in a while. In fact, it may be deserving of the coveted MajorHiFi Gold Award.

You can find the InEar ProMission X for the best price here:

InEar ProMission X at Audio 46

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Gabby is a composer, songwriter and music producer who has worked in the music, film, and commercial industries for too long. You can hit Gabby up at