Thieaudio Legacy 4 Review - Bright Ideas

Thieaudio Legacy 4 Review - Bright Ideas

Review written by @Precogvision


Thieaudio has been making waves in the IEM community this year following the release of two very successful IEMs: the Monarch and Clairvoyance. Personally though, I haven’t had the chance to hear these IEMs yet, and their other IEMs I’ve heard - the V3, L3, L9, and V14 - have left me more milquetoast in my reception of the brand. Yes, as usual, say hello to your friendly contrarian reviewer. But there’s a first time for everything, and once again, word of a new Thieaudio IEM has been making rounds, even winning the praise of closely trusted ears. Consider this reviewer cautiously optimistic to see what the L4 is packing. 

This unit was kindly provided free of charge for review by Linsoul. You can purchase the Legacy 4 here. As usual, what follows are my honest thoughts and opinions to the best of my ability. 

Source and Driveability

All critical listening was done off of an iBasso DX160 (volume ~10) and an A&K SP1000M using lossless FLAC files. The stock eartips and cable were used. I had no trouble driving the L4 off of any of my devices, and I did not experience any hissing.  

Thieaudio Legacy 4 |

The Tangibles

Thieaudio has constantly been upping their presentation game, and I have to say, I think this is the best yet. You’re presented with a large, hard-cardboard package with the brand’s name boldly emblazoned on front. On the back, the IEM’s specs and an image depicting the frequency response graph are included; it’s great to see more manufacturers including them in the interest of transparency. The following accessories are included inside: 

  • Assortment of silicon eartips
  • Soft carry case
  • Large carry case
  • 0.78mm 2-pin cable

Thieaudio Legacy 4 Unboxing |

To be honest, I’m not sure what I’m going to do with the large, soft-carry case, but hey, it’s cool. The small, soft-carry case is also on the larger side for pocket-carry; however, it’ll go nicely in a backpack or other bag, providing sufficient protection for the IEM. The cable is lightweight, pliable, and of good quality. In fact, I liked it so much, I even swapped it over to my 64 Audio Nio! 

The L4 itself follows a similar physical design to that of the L3. Those with smaller ears should be in the clear; of course, your mileage might vary and all that. The faceplate depicts a more muted aesthetic, but with some swirls and glitter mixed inside - it certainly looks quite impressive from up close. I believe Linsoul has also recently added an option for custom faceplates at a small upcharge which is awesome! Oh, and this might be a bit random, but the new logo looks a lot better than whatever tacky font the old logo was using. Overall, I’m very pleased with the presentation and the build quality of the L4 itself. 

Sound Analysis

Frequency response measured off of an IEC-711 coupler. There is a resonance peak at 8kHz; as such, measurements after this point should not be considered reliable. 

Thieaudio Legacy 4 Frequency Response |

The overall tonal balance of the L4 can be classified as a mild V-shape. The L4 has dip-switches which can be used to adjust the tuning, but there are technically only two different tunings as opposed to the expected four. The second tuning (01/11) stacks on some more lower-midrange presence while also raising the upper-midrange in an effort to compensate and prevent it from being inundated. If you’re listening to a lot of male vocalists, or simply enjoy some more warmth, fullness to your sound, then the 01/11 settings are what I’d gravitate to. I’ll mainly be speaking for the stock tuning though, as the second tuning characterizes a level of forwardness that quickly fatigues my ears. 

Let’s talk about the good stuff. The L4’s new 8mm subwoofer is a marked improvement over the one used in the L3, and gone is the overly blunted transient attack and horrid smearing of macro-detail. The first time I gave the L4 a listen, I recall playing Illenium’s “Broken Ones” - a fairly quick, bass heavy song - and thinking to myself, “Wow, this thing slaps”. While perhaps not quite to the level of control that the venerable Etymotic ER2XR exhibits, I hear good amounts of texture and slam; needless to say the L4 has some of the most pleasing bass tactility I’ve heard at this price point. 

...however, before I get too shilly, allow me to interrupt your regularly scheduled programming with my hot take on the L4:

Unforgiving Explication 

A.K.A. I moan and groan about why the IEM in question fails to meet my high standards, why you maybe shouldn’t purchase this IEM, and the section of the review you’ll want to skip if this type of more critical talk offends you. But you’re not going to, right? ‘Cuz this is the juicy, important stuff. 

So subjectively (that is, even more subjectively), I’m not completely sold on the L4. Issues with the tuning start cropping up as we move into the midrange and treble, and like so, it’s one of those IEMs that sounds great to me on first listen, but that quickly becomes fatiguing. Why? Notice how the L4’s ear gain exhibits a plateau from 2-3kHz. This is important because it largely dictates how “forward” vocal presentation sounds. My own preferences are more laidback, and they most definitely do not plateau like that. Stack on a 5kHz lower-treble peak and what sounds like a good deal mid-treble (in contrast to what the graph might indicate), and the L4 is excessively bright to my younger ears. To be clear, and lest I be pegged unfair, this is not a criticism of the quality of said treble so much as it is the sheer quantity

...and detour aside, we return to my kinder thoughts: 

In this vein, treble-heads will likely enjoy the L4. I hear good impact and crash; to reiterate, more than what the graph might imply considering the subsequent dip after 5kHz. This is especially apparent on the second setting (the more “forward” of the two), and you can imagine that my aforementioned issues are only exacerbated using this setting, but I digress. Like most IEMs in this price range, the L4 does not exhibit the best treble extension; however, I think it has sufficient presence in the post-10kHz frequencies to keep things from feeling too closed-in. I’m even willing to go so far as to say the L4’s treble is “above-average” for the price point, and all the more so if you’re a treble-head. 

Technical Performance

For the price, the L4 is a strong technical performer. Resolution is a standout, a step ahead of the Moondrop KXXS, my usual $200 benchmark, while perhaps not quite to the level of the Etymotic ER4XR. More than likely, this is where the benefits of the 2-3kHz plateau and the 5kHz treble peak are coming into play, as the perception of resolution can be created by boosting the aforementioned regions. However, I also frequently make a distinction between resolution and detail retrieval. Like so, I was pleasantly surprised by the L4’s latter ability. It might just be a consequence of the L4’s lower treble peak, but it does seem like the L4 captures smaller nuances better than its price might imply. For example, I can hear the faint rattle/chirping in the backdrop of Taeyeon’s “I Found You” which many other IEMs at this price point obscure. 

It’s on the layering side of things that the L4 begins to struggle; this seems to be a prime limitation of many lower driver count BA setups. Notes have a tendency to squeeze on more complex tracks, resulting in “confusion,” as if the IEM isn’t quite able to keep up with everything it’s processing. Along these lines, positional accuracy is average, and diffusal of the image falls inline with only slightly more headroom than the price point might give credit for. 

Select Comparisons

Thieaudio Legacy 3 - $120

Admittedly, I didn’t like this IEM very much. The tonality was pleasing enough; however, the L3 had serious issues on an intangible level. Smeared bass transients, smothered treble, and by extension, excessive BA timbre, it really was not my jam despite the accolade of rave reviews it received. The L4, then, is an improvement in almost every regard to my ears. As I alluded to earlier, the bass is much cleaner, and many of the technical deficiencies of the L3 have been addressed. Definitely consider dropping the extra coin for the L4 if you can afford it; of course, be aware they have different sound signatures (the L3 is a much darker IEM by comparison). The Voyager 3, though? It isn’t even in the equation here.  

Moondrop KXXS - $190

The KXXS is tuned to the Harman target curve and can be considered something of a mild V-shape like the L4 but with less sub-bass and less treble presence. In tandem with its transient attack which takes on something of a pillowy-ness to hits, it’s a warmer, more laidback listen. By comparison, the L4 prioritizes clarity and takes on a more in-your-face presentation; the L4 has a solid technical edge in resolution and imaging. Nonetheless, I’ll be the first to admit that I prefer the KXXS. It’s more pleasing to my ears on a tonal level, and the coherency and timbre benefits of a single DD are more my jam. But definitely go for the L4 instead if you want the better IEM on paper and like what I’m describing. 

Moondrop Blessing 2 / Dusk - $320 / $330

I get asked to compare these quite often, so here we are, and oh man, I have to break some hearts again. First, just to be absolutely clear: This is not a fair comparison, as the B2 and Dusk are literally a hundred dollars more. Both IEMs - particularly the Dusk - are tuned better than the L4, although I could see the L4 coming for the B2 in some respects. It’s the intangibles where the B2 and Dusk distinguish themselves most from the L4, though. While the L4 comes close in terms of sheer resolution, it falls short on the more latent stuff by comparison: layering, imaging, macrodynamics, the works. That being said, if you’re a basshead, you’ll be pleased to know the L4 has better bass (texturing, slam, tactility) despite the B2 and Dusk also using a dynamic driver.

Thieaudio Legacy 4 |

The Verdict

As a reviewer, I am often compelled to look beyond the scope of my wholly subjective and more, ah, pedantic scrutiny. And no doubt, my frame of reference might not be best for approaching these types of IEMs. I am, after all, but a product of my time as a reviewer, a time in which we are experiencing a golden-age of sorts for IEMs. 

Along these lines, a year or two ago? The L4 probably would’ve been the hot IEM to buy; heck, it might’ve even been groundbreaking. For now, though? The L4 will have to settle for being another very solid contender in the $200 bracket, one that unmistakably merits its price. I think it nicely follows up on not only the success of the Thieaudio twins, but also on more antecedent products like the L3 and V3; I’m pleased to recommend it bearing some minor caveats. 

Reference Tracks

  • Aimer - Hakuchuumu
  • David Nail - Let It Rain
  • Dreamcatcher - Silent Night
  • Illenium & Excision - Gold
  • Girls’ Generation - Galaxy Supernova
  • Joe Nichols - Sunny and 75
  • Keith Urban - Defying Gravity (2009)
  • Sabai - Million Days
  • Sawano Hiroyuki - Best of Vocal Works Remastered (2020)
  • Taeyeon - My Voice (2017)
  • Tiffany - I Just Wanna Dance
  • Tom Day - Where Were We



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