Ah, Sony. Among the popular audio brand in the enthusiast scene I have heard nowadays they are if anything, one of the most bizarre companies behind the scene. But undeniably, Sony has proofed that their work with Audio isn't just for flaunt, especially their IEM. The MDR-EX1000? The IER-M7/M9? or even, Sony pinnacle of their audio engineering: The IER-Z1R. All are some notable products that keep the company relevant in the community to this day.

Of course, I am not outside of this chamber alone, as the IER-Z1R has been one of the IEM that I have been wanting to own since last year and managed to achieve this goal upon my move to Japan. But I digress.

In these recent years, Sony has been applying its Audio resources to the True Wireless department and it does show. Specifically, the WH-1000XM3/XM4 (for headphones) and WF-1000XM3 (for IEMs) are still on the consideration list of a lot of users when they are planning to buy a TWS audio product. And now, as the WH-1000XM4 being released, it comes as no surprise that the IEM portion would receive the same treatment with the WF-1000XM4.
After several days of visiting E-Earphone to try out this product. It's time to bring to light the question that a lot of people in this Audio hobby would ask: How does it sound?

Before going into the post, if you are new, please read this before having any comments regarding my writing or point of view‌.

Special note for the newcomers: This article would be heavily focused on the Sound quality part, if you are reading this hoping for me to break down the glory Noise canceling, battery life etc... feature(s) Feel free to look for someone else.

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All of the impression is done with Demo samples provided by E-Earphones. Though the measurement are from external source


I planned to skip this part as an article like this usually means that the sample I tried isn't something I am owning (or having on loan) right now but since some of the audience coming to this article isn't just looking for sounds alone, I will make a small exception.

Let's get started with this picture

Sony WF-1000XM3 and Sony IER-Z1R

Now, for the people who aren't familiar with the Audio enthusiast scene, let me fill you in first. This is an image of the WF-1000XM4 by the Sony IER-Z1R. For people who don't know the latter (and skipped my introduction): currently, this IEM is one of the most expensive offerings that Sony has - spotting at an MSRP price of 2000$.
But, let's disregard that and focus on the main topic: one thing you should know about the IER-Z1R that besides their critically acclaimed sound quality from the community, is also the notorious problem of this IEM is in its size.
Yes, this thing is not just heavy but big. The fit problem was popular enough that you can easily find some people in the hobby that cannot stand having this thing into their ears for more than half an hour.

And that's why I made this comparison with the WF-1000XM4. The size of this IEM if anything, is as big (or slightly bigger) than the Sony IER-Z1R itself, so people with small/medium ears might have to beware of its fit, especially compared to a wired IEM, a TWS rarely have an ear hook that helps distributing the weight.
Thankfully though, comparing to the IER-Z1R, the WF-1000XM4 is at least, not a huge chunk of metal. Hence, the IEM is pretty light so most of the concern would be the fact that if it can stay into your ears when you are moving or not.
Still, I reckon this situation isn't new considering the XM3 is a thing, its fit would still be one of the major things to note for people who are looking for a TWS for daily convenience.

Sound Analysis:

This impression is based on the stock sound of the IEM. Done at Firmware 1.1.5

This impression is also based on the Noise canceling mode as well due to better sound quality.

The XM4 as far as I hear, follows a Neutral signature with a boost in the bass. Though I can see someone regarding this as a Neutral-warm signature as well due to the lower-mid boost that this IEM has (which you can see on the graph below, and yes, this is somewhat evident on all EQ preset if anything).

Sony WF-1000XM4 (Noise canceling) Frequency Response - Can be seen from the Frequency Response Index

Let's start with the first major concern of the XM4 that the enthusiast community has this time around: Its treble.
This is undoubtedly one of the aspects where most people within my circles immediately react due to the roll of from 3kHz from the measurement, which usually results in a dark, unengaging presentation. And to be honest, they aren't far off on this front: the WF-1000XM4 most problematic aspect lies in this region alone, though I don't think it's that destructive.
Take instruments like cymbals and hi-hats, and I immediately notice their presentation taking an interesting turn: Lacking presence on the stage, yet, weirdly retaining some shimmering just to reminds me that these instruments aren't entirely lost.

Hence, I don't think this would be the factor that made the XM4 being a bad IEM after hearing it, and while I am at it the other region of the frequency responses is decently done in contrast.

Nothing much to say on this part. The WF-1000XM4 sounds quite balanced in these two as a whole. Maybe just screwing towards the warmer side but that's all. Vocals seem to take the spotlight of the stage of this IEM, with enough forwardness that would be contempt for most people though being picky myself I would want them to have a 2 - 3dB boost at 2.700 Hz. The bass also doesn't get too overwhelming, if anything, it is kept relatively clean while reaching quite deep into the sub-bass region.
Overall the WF-1000XM4 performs well against stringed instruments like Cello or Violin, though the roll-off mentioned above did kill some of the air of instruments like Flute - still not too bad though.

And switching to the technicalities part I think I do get a sense of the sound direction that the WF-1000XM4 is trying to gear towards here - smooth, pleasant. Note decay seems to be rounded off, creating a sensation of smoothness that fits for a long-term listening session. Though in contrast, this takes a hit on the IEM overall resolution which not something for technical listeners but this is a TWS anyway.
Were if I am trying to take a jab with this IEM is that there is some sense of haziness on the presentation of the track, and to even put it bluntly. I had joked myself of Sony ripping the driver from their XBA series into this IEM (Which highly isn't the case but still)

Other than that, the XM4 did well on its imaging/staging part. There is some sense of depth in the sound field, instruments are well separated even comparing to the grand scheme. Were if there is a bit more width on its stage then I would confidently grade this as above average.

Quite a decent TWS overall sound-wise, but there is a little problem...

Being outclassed by the WF-1000XM3 in terms of engagement factor:

Sony WF-1000XM4 vs Sony WF-1000XM3 Comparison graph (Normalized at 1000Hz) - Comparison can be done at the Graph Comparison Tool

Were if there is a reason why I would put the XM3 on a slightly higher note than the XM4 based on their stock sound alone, then it would be that the XM3 is a more enjoyable IEM.

  • The XM3's bass have punch, and the rumble is satisfying due to the boost comparing the XM4
  • The XM3 has more treble presence than the XM4
  • The XM3 has a clearer note presentation and slightly more accurate in terms of positional cues. (Note that I had listened to 2 XM4 samples to come to this conclusion)

Out of these three, while I observe people posing concern with the treble performance, I am slightly irritated about the technical performance outclass. But I digress.

So what does this mean then?

First and foremost, I am not saying this just to make the XM4 look bad, a presentation that is more "neutral" is appreciated. But, if you are a current WF-1000XM3 owner who likes its sound presentation, you might have to beware of this aspect if you planning to upgrade. Unless EQ might do something with this which is a possibility since I suspect Sony TWS are DSPed anyway. ‌‌‌‌‌‌‌‌

And speaking of which...


Note: Due to my reviewing methodology, this section won't contribute to the final recommendation rating
Also, for people who doesn't care about EQ, you can skip this, this article is done over this section.

Giving that Sony also includes Equalization with their app, I figured out I will take the chance to fiddle with this anyway. Overall, the Equalizer that sony built through their app is a 6 fixed-band equalizer, so expect these bands would only be enough for minor tweaks here and there compared to the type that gives you full control like a Parametric EQ.

That said, despite being only 6 bands, Sony included a total of 8 premade presets, which is a lot.

Sony WF-1000XM4 frequency response of various EQ presets - Comparison can be done at the Graph Comparison Tool

My apologies if this turned out to be a bit messy to look at (This is 8 presets after all), you can check one individually through this page. Though I will still provide the list here:

  • Red: Excited
  • Lime Green: Bright
  • Purple: Speech
  • Sky Blue: Mellow
  • Yellow: Relaxed
  • Green: Vocal
  • Dark blue: Bass Boost
  • Orange: Treble Boost

Now, it would take ages for me to list my impression for all these 8 so I will exclude some of the ones I dislike the most which are: Speech, Mellow, Relaxed, and Vocal.
All three on the first of this list are nothing but making the sounds muddy. As a result, I had to strain my ears just to find the last bit of energy in my playlist. Vocal preset isn't as bad but the presentation is more boxy than muddy.

With all that said, among the decent ones, the two I found most interesting were Treble Boost and Bright, with the two going close to 2 academic targets known in the hobby nowadays.

Treble Boost EQ:

The Treble Boost preset follows close to the Harman Target, one of the preference target that some IEM companies have been adopting in their tuning methodology. Though for people who aren't familiar with the hobby, you can find TWS following this tuning style in the Samsung Galaxy Buds, any of the Buds would do.

Sony WF-1000XM4 (Treble boost EQ) and Samsung Galaxy Buds+ against Harman 2019 Target (Dotted line) - Comparison can be done at the Graph Comparison Tool

Now, while there are some parts of the Harman Target that I quite prefer, I just don't like how over-excited it is. And well, the Treble boost preset is basically that. The entire sound presentation is real excited, crispy. But, one thing I solely detest about this preset is the upper treble spike.
This preset boosted the 16kHz band nearly to the max, bringing an irritating sensation that reminds me of the Tin Hifi P1. Hence, the IEM now is coated with a timbre presentation that is metallic and can be too much for some of my casual tracks. Though, this is one of the worst offenders:

Not really something I would shove Japanese music in. Though removing that aspect, it's by far my favorite premade preset. Not because it sounds so good, but because it's better than all of the preset I tried.


Contrary to the Treble boost EQ, I think this is not as bright. That said, this preset follows closer to a Diffuse Field type of tuning, with a twist of warmth due to the bass shelf.

Sony WF-1000XM4 (Bright EQ) against Diffuse Field Target (Dotted line) - Comparison can be done at the Graph Comparison Tool

This one surprisingly is not too bad despite how wonky it might look for some. The upper-mid boost does make female vocals come out as more forwards than it necessarily does though.

Excited and Bass boost:

Sony WF-1000XM4 Bass boost EQ vs Excited EQ - Comparison can be done at the Graph Comparison Tool

The reason why I group these two is because of one thing: Bass

Both of these preset focus on putting the Bass response as the central of the track. Though to be blunt, Bass boost EQ took this a bit too far. The boost basically was too much for the driver to handle at my listening level. As a result, the bass presentation is just straight muddy due to the transient/distortion.
The Excited preset is a different story, as the bass got boosted, it also offset the "already problematic" treble even more. However, it's not bad though and I can see someone jamming this preset to bass-heavy songs (more than the Bass Boost EQ does due to the technicalities). But, if I am going for this bass shelf I would rather be bumping up the upper mid and treble a bit.

With all of these being said, I did fiddle with the Manual EQ mode also so...

Manual EQ to my preference target:

Sony WF-1000XM4 (Manual EQ) against Banbeucmas Target (Dotted line) - Comparison can be done at the Graph Comparison Tool

One funny thing I found with this EQ is that the resonance peak at 8Khz was too small that the response curve lined up perfectly with the Target, but I digress.

For anyone curious about this EQ, here is the setting I did:

Bass: 0
400Hz: 0
1000Hz: 0
2500Hz: +2
6300Hz: +4
16000Hz: 0

I think I don't have to say anything about this EQ, overall... it is tuned to my preference. If anything, my only jab is that the XM4 still has that timbre issue of being Metallic though admittedly isn't as bad as the Treble boost preset.
This is probably due to the amount of lower treble in this earphone along with the decay in the transient that is creating that sensation. Though, I am not wholly convinced by this theory.


With a hefty price tag of about 280$, is the Sony WF-1000XM4 worth it?
Probably, probably not. From what I can see from the TWS market though, the XM4 overall is a decently made IEM all things sound related considered, but then with the existence of the WF-1000XM3, it's hard for me to say that the XM4 is a hard recommendation/upgrade based on its sound performance alone.

Though, again, this is a TWS, with other features that a consumer needs. My job with this article is only to provide the perspective of a person who is into Audio. For the rest of the fancier feature, I will gladly pass my mic.

Edit 1: I am in process of rechecking the graph I measured yesterday due to a problem with REW in tablet mode (which can make me mixing up the graph legends). Will do the necessary change later. Post updated

Recommendation ratings: Niches