Thieaudio Legacy 4 Universal IEM

General Information

1DD + 3BA Hybrid In Ear Monitor
  • The proprietary 8mm poly-membrane dynamic driverKnowles TM and ThieAudio Customized Balanced Armatures 3-Way Crossover Network is integrated into a 2-switch tuning system Paired with an OCC 4-core custom cableUpgrade EST cable is 2.5mm balanced cable comes with 3.5mm and 4.4mm adapterHand-crafted, tested for Quality Assurance

Latest reviews


Headphoneus Supremus
Thieaudio Legacy 4: Swirly looks, good sound; what more do you want?
Pros: Gorgeous looks.
Good fit.
Accessories, accessories, accessories
Sound, which while tunable still provides for a pleasant listen
Tuning switches worked for me
Good detail and air of note
Cons: Not quite enough bass
May sound "thin" to some
Some say switches are for show only
Extremely tough price point
Some may not like those gorgeous looks
Thieaudio Legacy 4 ($195): Swirly looks, good sound; what more do you want?

When Lillian contacted me about reviewing the Legacy 4, I accepted her invitation without hesitation. Having read a wee bit about the line, I knew the sound was getting good reviews. Not the hyped flavor-of-the-month type but real respect for everything from the builds to the sound. This is my first Thieaudio model and based upon my initial reactions and the deeper delve of long listening, I hope it is not my last. This is an excellent start.

I thank Lillian and Linsoul for the review sample. An open, honest review will be forthcoming. The unit is understood to be mine, unless asked back for; and may not be sold for a profit as that still remains a really uncool thing to do.

Legacy 4



Thieaudio was launched in 2019 as a creative endeavor of Linsoul Audio. The goal of Thieaudio was to serve as a creative platform for gathering the best teams of engineers to inspire revolutionary audio products for audiophiles and professionals alike. For each project, we hand select the most innovative and renowned engineers in his or her field to oversee the design, engineering, and manufacturing of the products. Gathering the momentum from the success of the Thieaudio Phantom planar magnetic headphones, as well as the Voyager, Legacy, and Signature series In-Ear Monitors (IEM’s), we are committed to the continual expansion on the limits of high-fidelity audio. We welcome you to join us and experience excellence in musical performance.

Legacy 4 innards:

The proprietary 8mm poly-membrane dynamic driver
Knowles TM and THIEAUDIO Customized Balanced Armatures
3-Way Crossover Network is integrated into a 2-switch tuning system
Paired with an OCC 4-core custom cable
Optional Upgrade EST cable is 2.5mm balanced cable comes with 3.5mm and 4.4mm adapter
Hand-crafted, tested for Quality Assurance


More intro information:

Legacy 4:
The Legacy 4 was designed concurrently with the Legacy 5 to provide a unique twist to the lineup. With the beloved budget model, the Legacy 3, and the natural and smooth sound signature of the Legacy 5 in mind, we wanted the Legacy 4 to be a middle ground - both in terms of the tuning and price. Utilizing a completely new in-house 8mm poly-membrane dynamic driver for the low end, the Legacy 4 provides the impactful slam of the Legacy 3 and 5, but with a faster speed and enhanced texture. This new driver matched with the tried and tested American Knowles ED29689 balanced armature (BA) and intuitive low-mid passive crossover design emphasizes a natural mid-frequency presentation. With a less aggressive crossover design than the Legacy 5, the mids of the Legacy 4 presents a more musical experience that ever so slightly adds a dash of warmth to the overall signature. With the partnership of Bellsing, we have developed a custom dual BA tweeter for the Legacy 4 that perfectly fits the mid BA driver. From the relaxed and smooth treble delivery of the Legacy 5, we have tuned the Legacy 4 to bring more upper treble presence, highlighting upper frequency overtones and details. This tuning and the extremely capable treble extension of our new tweeters brings an even greater level of airiness and shimmer to the mix, making the Legacy 4 an excellent IEM for both professional musicians and music enthusiasts alike. You can trust that the Legacy 4 will provide one of the most natural, accurate, and enjoyable musical experiences among any IEM’s of its class.


Model: Legacy 4
Frequency range: 20Hz-20KHz
Monitor Plug: 3.5mm
Connector: 0.78mm 2PIN
Sensitivity: 108±0.5db
Impedance: 9.4Ω
Noise isolation: 26dB
Detachable cable: 120cm

Gear used/compared:

Unique Melody 3DT ($399)
Oriolis Finschi ($179)
BQEYZ Spring 2 ($165)
DDHiFi Janus ($199)
Shozy Form 1.1 ($75)

Shanling M6 Pro
Cayin N6 mk2ii
HiBy R3 Pro Sabre


Dave Matthews
Joey Alexander-Warna album and others
Mark Knopfler-Laughs And Jokes And Drinks And Smokes
Santana w/ Mana- Corazon Espinado
twenty one pilots
Tedeschi Trucks Band
Big Head Todd & The Monsters-Beautiful World
Mark Knopfler-Down The Road Wherever
Elton John-yep, still good, still cool
Tidal MQA



Coming in a fairly small black rectangular box, the front is laden with the “THIEAUDIO LEGACY 4” words, and a graph on the back. Understated, especially after the box is opened. Once unlidded, you are met with a gray tweedish colored case that is almost as big as the box itself. Unzipping the semi-hard case, which has a protected zipper cover, you are met with another smaller case in which the included cable lies. Nestled in shaped semi-hard foam to the left are the gorgeous IEM’s. Below that you have a SOLID 4x credit card thick piece, replete with pegs for the included tips. It is actually held in place with Velcro tightly wrapped around it. I had a really hard time returning the Velcro around the board, so I tucked it under the aluminum. That aluminum also fits in very tightly to its requisite space.

A nice feature of the case is that the foam piece, which holds the IEM’s can be removed and a small to medium-small DAP can fit in there nicely. You could even place a larger DAP in place of the smaller case and have the Legacy 4 & cable to the left. I will admit I was not expecting two cases, let alone one so large. Frankly, the smaller case is what I will use mostly, but the larger case will hold other things such as extra tips, or cables. A nice addition to the kit, regardless.


Tuning Switch:

From the website: The Legacy 4 crossover network is integrated into a 2-switch tuning system that allows the user to define the level of bass and mids. This tuning system means you can find the perfect sound signature no matter your musical preference!

With both switches down, you get the “natural” sound of the IEM. Switching the left one up on both IEM’s, is for an added benefit of bass tuning. Reaching a bit deeper, with a good thump as well, this would be the preference for bass loving people. Switch the right one up only, and you enhance the mids, while the bass response becomes a bit withdrawn. Pushed forward, the vocals sound quite good but to me a bit too far forward. With both in the “on” position, you get enhanced bass and mids much like adding a quick fix of EQ, but to me the mid switch overrode the bass addition. For my testing, I left the left switch up as my preference.

The switches themselves are quite small, and I carefully used a bent paperclip to change. A system much like Dunu has on the SA-6, which can utilize your hand on the fly is a better choice in my mind. Regardless, the switch allows you to somewhat tailor the response of the 8mm dynamic driver and custom Knowles ED29689 balanced armature as well as the two Thieaudio balanced armatures. Stated as having a less aggressive crossover than the Legacy 3 or 5, the 4 sounds quite smooth across the spectrum, regardless of switch position.



One cannot help but be drawn to the IEM first, as it is highlighted in the upper left. Made from medical grade German resin, each pair is unique, since they are hand poured. As stated in another review, the look is stunning as well as unique and becoming more in vogue. I do appreciate this look since most of them are understated in their elegance and not garish in the least. Each earpiece is also matched to provide the closest pairing, tuning-wise possible.

The shell itself looks like a semi-custom shaped shell of semi-transparent greenish gray color. The insides are highlighted nicely as a result. I will admit that upon first look, I immediately thought I may have problems with fit, due to the protruding knob behind the nozzle. I did not. With a vent hole in top, including laden with a bronze colored insert, tuning of the lower end is helped by said vent.

Over the years I have come to appreciate looking inside the shell, when done properly. And the Legacy 4 is done properly. You can see the drivers, and the configuration. With sound tubes coming off of each, the balanced armatures are “herded into on tube, and the dynamic driver into another. As a result, there are two opening on top of the semi-short nozzle. The nozzle does have a slight “lip,” which helps holds tips in place. I tried both silicon and foam tips but stayed with the stock silicon tips throughout the testing.

The faceplate is a swirled cacophony of color, and as stated my pair is of an understated elegance, which appeals to me. A mix of copper, white, gray, blue, and sand-like sparkles surround the cat eye-like look of the middle. With a 3-D presence, the faceplate looks stunning. Under direct light you can imagine the 3-D layers of color as waves on an ocean, as the silver “THIEAUDIO” lettering takes on a subtlety not had when direct light is not on the unit. Under normal circumstances, the lettering is prominent but still understated. Shine a light on the shell, and the character changes. Nicely done.

The only “flaw” I could find is that the 2-pin cable does not lie flush against the shell when inserted. Both are pushed in all the way, but not flush. I also noted that one was considerably harder to push in, but I managed carefully.

The cable is 4-core OCC custom of 120cm length. There is a bit of tackiness to it, but the cable lies well, without tangle nor microphonics. Not wound overly tight, I never had a problem with tangling or snagging. The 3.5mm se jack is silver and straight, of good thickness as well. There is no over-ear guide, but a bend allows the cable to sit without bother even with my glasses on.

Once inserted, I had no problem (not that I had a problem inserting the IEM...) with fit or placement, as the Legacy 4 did not bind or fit at an odd angle. Sitting nearly flush as well, the Legacy 4 is an unobtrusive IEM, too. Using the silicon tips, seal is quite good with only a minor bleed into the ear cavity from outside noises. Once the music starts, all is good and right in the world.

The quality of offerings at this price continue a trend of excellent build quality that until recently was afforded only in the much higher price brackets. I am over the top excited this trend continues to trickle down the price level.



From the beginning, I was impressed with this affordable mid-fi entrant. Providing a fairly rich, and deep bass set the tone for near-silky smooth mids, with vocals that played very well with the warmth provided. Guitar work cut right through any perceived veiled character (there wasn’t any), just to let you know that this plays well. Plus, with a top end that does not offend me, even with both switches set to the “on” position; there was much to appreciate from the Legacy 4. If I had to glamour a prominence, it would be that the mids take the heart of the show, moving a bit forward and a bit up, but not in an offensive manner. Think of the drum major who goes about their business in a well, business-like manner and that would be a good assessment of the mids. This IEM seems to be working its way up the food chain of $200 IEMs as a result.

Again, that bass is present in enough amount (left switch in “on” position) to warrant respect, but not enough to push you into the rumble territory. Using the very good stock cable first (then a 2.5bal Effect Audio Ares II cable), I appreciated how succinct and tight the bass was, with decay on the faster side. There is good speed here as a result, which lends and air of authority and command that a slower decay might turn into a near-muddy mess.

The mids are to me the highlight, though. Clean and with a certain crispness, which accompanies the taut bass, guitar work is as succinct as the lowers, with a precision that works without being too airy or dry. I would not describe the sound as “wet,” as I’m not even sure what that would be other than rich, warm and vibrant; but use those three adjectives before the semi-colon and that would be an apt descriptor of how I hear the mids. The sound is developing into what I would say is akin to what the Finschi does for Oriolus: provide an excellent intro into the world of Thieaudio.

Since I left the left switch on, and the right “off,” I will use that as the baseline for the treble sound. A good feeling of air between the notes is had up top, without becoming disjoined from the other aspects of the sound signature. Clarity of that air is ever present on such songs as Ottmar Liebert’s Snakecharmer. A certain staccato of sound emanates from the uppers, which is both clean and refreshing without being thin or hollow. A certain delicacy of sound comes forth as a result of the treble tuning. If I had one wish regarding the three sections mention here, after a bit more bass thump it would be a slightly higher push of the treble note. Which if you follow my other reviews is a turn the opposite direction since I do not like too much push up top. Let’s simply ask for a bit more sparkle up top and this would be the excellent complement I wish for. Turning the right hand switch up only pushes the mids a bit more forward and up, like a 6dB push might from a good EQ. Therefore, I can happily live with tuning as such laid out.



Taken separately since I have addressed somewhat the airy separation of note above; the soundstage is neither large and expansive, nor narrow and small. I would say that this is about a cubic as any I have had of late, with the center point pushed slightly forward and up. Call it middle of the road if you wish, but I prefer to call it not wanting to intrude upon the other aspects. A common theme is developing: one of which the harmonic balance of all qualities with regard to the sound signature playing well together is coming forth. That is not to call this boring or middle of the road, but balanced and having no need to temper or intrude upon the experience as such.


As I mentioned above, speed and decay are quite good, which may seem a bit antithesis to the balanced signature noted as well. I do not think that would be the case, as the timbre gives that speed quality a decisive yet forgiving tonality that works to provide a reality to the sound, which is the intended result. It is one thing to be decisive and dry/analytical. It is another to be decisive and open/honest. That would be how I hear the Legacy 4. Balanced, decisive and good timbre representing that honesty of presentation.


Thieaudio Legacy 4 ($195) v Unique Melody 3DT ($399):

I start with the most expensive of those listed here for a reason. I made reference to the Legacy 4 in the 3DT thread as the pairs both arrived a day apart. This can be good and bad. Good for comparative purpose. Bad for deadline purposes. The other part of that is I also mentioned in the thread that I may like the “secret IEM” more. The secret one is the Legacy 4. And after thorough listening of both (the good part), I can hopefully pinpoint the differences and similarities.

First and foremost, I like both quite a lot. The fit of the Legacy 4 is easier on my ears as it is a bit smaller. To attain a good seal and sound quality I like from the UM, I had to use a spare pair of my Comply’s. Not bad mind you, but the comfort level is not on par as a result. I will quality that using the included silicon’s I had no trouble for long periods, and the sound was just fine. I wanted a bit more bass push, hence the Comply’s.

Next, and to me the biggest difference is that the UM provides a more mature sound. Richer of note, but also presenting a cleanliness that matches and slightly betters the Legacy 4 separate the two. Warmer tonalities (partly the Comply’s) help separate that maturity, but I am thoroughly impressed by the succinctness of note, which permeates the overall character of the 3DT. Considering this is the “entry level” UM, this is quite the fine bird. I have always appreciated the UM tuning as well. Bass when needed, and a quality of note that just hits me like a fine bowl of oatmeal, with pecans, Craisins and brown sugar on a cold winter’s morn. Steaming hot with my organic local cup of Joe makes for a wonderful setting. That is how I feel about the UM 3DT. It hits the right spot.

Calling it the big brother of the Legacy 4 would not be an insult, but something for the Legacy 4 to look up to, instead.


Thieaudio Legacy 4 ($195) v Oriolis Finschi ($179):

Mentioned often in my reviews, the Finschi is my baseline at this price, although some have come close (see those right below...). From my first listen, this set the tone. That was a bit over two years ago, and you can clearly see how time and tuning has proceeded. The Finschi bass is sublime in its presentation, tying to those slightly uplifted mids quite well. There is a bit of cover presented from the mids, which tames what could have been near-perfect mids, in instrumentation and vocal support, but hearing the newer models, you find that they may well have surpassed the Finschi. But here is where the others may still fall behind, including the Legacy 4: a richness of tone that is such sweet and succulent in representing the emotion of song. For that there is still no peer in this price to me.

For a wonderfully balanced signature, the Legacy 4 has surpassed the Finschi, but if you desire a warm, richness of tone for your pleasure, then there are still few, which can match or surpass the Finschi in this price to me.

Thieaudio Legacy 4 ($195) v BQEYZ Spring 2 ($165):

Like the name (yes, bad punnery coming...) the Spring 2 is a breath. A breath of clean, clear and crisp air. The Spring 2 has a much more open sound than the Legacy 4 and a certain lilt of which I like very much. This is a wide-open fun sounding IEM, without being frivolous or too carefree. What might be lost in detail retrieval is more than made up for in its airy presentation. Yes, usually with clarity and detail comes a certain airy presentation, but here the Spring 2 is slightly behind the Legacy 4 with regard to detail retrieval. But then again oh my, that fun sound!

The spring 2 is the IEM, which you would bring on your commute to lift you up in the morning, or that Friday afternoon commute IEM, knowing you have the weekend at hand. The Legacy 4 is the one to get you through the work week, knowing you can count on its speed and detail for accuracy. I like both, and they complement each other quite nicely.

Thieaudio Legacy 4 ($195) v DDHiFi Janus ($199):

I admit no fault in liking the DDHiFi lineup. None at all. I have yet to find something in their line of wares, which is not only functional but also fills a niche of need nicely. The C2020 case is my daily carrier of DAP’s x2 and enough of what I am testing to keep me happy.

Innovative and at the leading edge of much in which I love, DD did it again with the Janus. I opted to wait for a production model, as I felt my ears were not worthy of tuning such as others are and were at the time. I am glad I waited. The finished product is as fun as the Spring 2, but with an added benefit of a slight touch of warmth and richness of which I value in my listening pleasures. I am still torn between using the Janus up or down, and thankfully have both the Air and Forest, so both are in use often.

As for comparing to the Legacy 4, there is a bit less bass push, but the speed of decay in the single dynamic driver is impressive, nonetheless. Vocals and mids are pushed forward as well but are not as clean as the Legacy 4 (using Comply tips on both). But moving upward, there is a that bit of sparkle in the Janus, that I desired in the Legacy 4. So, this really is a wash. If pure sound is your goal, both are good choices. If you want a bit better air and fit, then the Legacy 4 would be the choice here. A bit more sparkle and a fun-factor? Then the Janus is the choice of these two.


Thieaudio Legacy 4 ($195) v Shozy Form 1.1 ($75):

I included the Shozy because it is my favorite Shozy to date. Even more so than the AAW-Shozy combination. For the price, the Form 1.1 is really quite hard to beat, and as another contributor @B9Scrambler notes; moving up to the Form 1.4, while good may not be needed because the 1.1 is so good. I would agree, hence the inclusion.

With a slightly “pinched” mid, that pushes the vocals and works such as guitar music more forward, the 1.1 is not what I would call shouty or in your face. Rather I would call it the fruition of fun-forward delight. It does not have the push down low of the Legacy 4 either. But no matter, the sound provides a rich, vibrant tonality that accompanies that mid push nicely. Add in some sparkle up top and you get a thoroughly satisfying sound emanating from a sub-$100 IEM. It is still amazing to me how Chinese fidelity has matured in such a short time over the last five years. To me the Shozy form 1.1 rode in on the forefront of that push towards higher quality and a more mature sound, that is balanced (not necessarily all, but many manufacturers thankfully lost that SHOUTY BIT, which annoyed many), providing a tempered treble note, and quality build to match. Good to see, and the 1.1 has the goods to back that up.

If it came down to the two though, the Legacy 4 fits my tonality more, with better speed and a deeper reach down low. Add in that the mids are so sumptuous and it really defines (or redefines to me) the category. The 1.1 is not shoddy in any form, but you see the maturing levels of the Legacy 4 show in the fruition of sound springing forth. Gah, what a fruity, flowering mash of a sentence. Apologies.



The Legacy 4 scaled well across many sources, letting the source be the definitive difference. Using the HiBy R5 Saber, the sound was a bit mellow, and somewhat thin. That is until I realized that the detail was the definitive aspect of what I heard. Concise without any slowness to it, Ottmar Liebert on Snakecharmer was succinct, detailed and crisp. That “thinness” of which I spoke actually came out as clarity. I did have to turn the volume knob up to fully appreciate the pairing, but still enjoyed the sound at near-minimal levels. This is a very good mid-fi pairing.

Switching to the Shanling M6 Pro, I immediately noticed the added verve of the dual DAC set up. Much more energy emanated from the duo, and there was a very nice rich tonality to the pair. Coming across as strong and vibrant, but without being bright or overly sparkly; the pair was probably my favorite. The Shanling is able to quickly alter its personality using the gain feature and single/dual-DAC features. A stunning performer, which added and complimented the Legacy 4 allowing the strengths to come out of both.

Having the iFi Zen CAN in for review as well has its benefits. I have used it for the HiFiMan HE-R10P as well as the UM 3DT along with the Legacy 4. Showing it can compete pretty darn well across the listening devices, it did pair well with the Legacy 4. I did find that when using both the XBass & 3D features, the sound became a bit loose. Bass overrode the overall quality and muddied the mids a bit too much on some songs. I still enjoyed it mind you but compared to the two DAP’s above it was a bit of a letdown. I count this as somewhat of an anomaly since the Zen CAN does sound quite good.



Going into this review, I was faced with another IEM in house at the exact same time. Once that is more expensive as well. I like both quite a lot and they are different enough to warrant a separate look. But, and here it comes, the Legacy 4 competed so well, that I liken this to the entry level IEM from UM or Oriolus. If the entry level IEM’s sound this good, what do the upper, more expensive one’s sound like? Don’t take this wrong. In fact, go the opposite way. If this model, the Legacy 4 sounds so good, do you really need to experience the upper end? This seems to be a facet of manufacturers of late; and that is good.

The Legacy 4 is not without fault (there is no perfect IEM out there, period. Only ones, which could fully satiate your desires...). It could have more bass for my taste. It is amongst the more tip dependent that I have recently had, and this affects placement in your ear and movement. I find with the wrong tip (even if it is my preferred listening poison) you must keep very still, much like Elmer Fudd stated so long ago, “be vewry, vewry qwuiet...we arwe hunting wrabbit.” But I tolerate it because the sound is so good.


Producing a model, which can completely satiate your listening desires at a price that is not that far from “budget Chi-Fi” makes you seriously think that while you could most certainly go further up the food chain, why would you though? And that is the defining decision, which makes me pretty much state that I have a “new king” at the $200 price range, supplanting my old king. To me, the Legacy 4 is so good, that you could define your collection around it and be happy to stay put. You really could. But what is the fun in that?

I again thank Lillian and Linsoul for the support and review sample. The legacy 4 is good and while it could certainly satiate your needs, I for one wonder what the higher ups sound like in the legacy line up. Cheers, and enjoy your listening.



New Head-Fier
Midsize car with leather seats
Pros: fresh and vivid signature
natural timbre
good technical characteristics
very good allrounder
Cons: needs good mixed music material to shine (not necessarily a disadvantage, as it rather speaks for the resolution of the IEM)

Perhaps a bit too much presence in the lower treble range for some
Rating: 8.8
Sound: 8.7



THIEAUDIO has quickly grown into an established company. Probably the most decisive reason for this is the tuner(s) behind the models, who always has the tonality in mind, but can also technically get a lot out of the chosen drivers. Despite different signatures, the individual models are mostly aimed at the general listening habits without great experiments (I exclude the Voyager 3).
The company (which is run under the patron Linsoul) knows how to convince in almost all price categories from 100$. However, I assume that a budget model (perhaps a single-DD) will be added to the portfolio in the future.

But back to the essentials. The LEGACY 4 is the fourth and currently newest representative of the series, alongside the L3, L5 & L9. Who has been missing with the L3, or L5 some energy in the upper mids and treble, gets this now with the L4. For me, an absolute value and tonal, but also technically a fantastic IEM in its price class.



IEM case in an accessory case (on-ear format), again in a box packaging. Unpacking the LEGACY 4 is a bit reminiscent of a matryoshka. The lush accessory case in particular is very unusual and of limited use when traveling, unless you want to take your portable DAC collection and 10 cables with you. "Unfortunately" the inlay is not removable and so you are somewhat limited in its use (toiletry bag, makeup case, Ü-egg collection...).
Nevertheless, this is of course nice to look at and makes a high-quality impression.

Yes, posh is the way the world goes down. The tip selection (exclusively silicone of one type in 3 different sizes with 2 pairs each) is presented impaled on a metal plate. The silver-plated cable is in the IEM storage case, along with a SIM card remover for dip switch adjustment.
The 8-core cable is quite good, though I found the cables of the L3 and V3 more satisfying to the touch. Likewise, I would have liked a 2.5mm (balanced) cable with a 3.5mm adapter. In this case, it is "only" a standard 3.5mm stereo connector. However, that can be changed with an extra $54, which is a bit high for my taste.

The L4 has a classic custom-style design and is extremely comfortable to wear. In addition to the ergonomics, the low weight and the size are also beneficial. Compared to the Moondrop Blessing 2, for example, it has much narrower sound openings and doesn't seem as bulky, which makes it suitable for smaller ears as well. The faceplate and body can be customized for a surcharge.

The workmanship is without complaint and the isolation is also quite good. However, you can't expect absolute shielding, since outside noise can penetrate better through the air vent for the bass. Nevertheless, the isolation is in a good range, even without music.

The L4 can also be made as a custom (CIEM). For this service, you pay $70 more if you can provide an ear impression.



The Legacy 4 has a warm fundamental tone with warm/neutral mids and slight brightness in the treble, which gives it a fresh but relaxed signature that takes its cues from HARMAN. In other words, a tuning suitable for the masses, which turns out to be a sovereign all-rounder and also invites closer listening due to the good technical characteristics. The description of the sound is based on the switch setting 0|1.

The low frequency is covered by a dynamic driver and scores with an extended bass and punch. However, it doesn't hit dry and too hard, but retains a certain softness that reflects a natural response of the bass and doesn't seem anemic or sterile. On the contrary, the bass adds warmth to the signature, which, however, does not contribute to falsification, but rather creates more of a natural body and solid foundation. The bass can provide fun depending on the genre and mix, but never overdoes it and does not fall apart even in faster passages. Still, I would like to see a bit more texture and precision. The low end is very reminiscent of the L3, though the L4 sounds a My tidier and tighter.

The similarity to the L3 cannot be denied in the mids either. Here, the bass (DD) harmonizes well with the midrange (BA), resulting in a warm/neutral tonality.
Since the L4 has a bit less level in the upper bass in contrast to the L3, the mids seem a bit clearer and not quite as voluminous, but this is also strongly influenced by more level in the upper midrange. This makes them sound a bit fresher and a bit more in-your-face, but without becoming garish or unpleasant. I particularly like the midrange's balancing act between assertiveness and simultaneous relaxation with tonal accuracy. Instruments sound natural and voices have a correct timbre, even if they sound perhaps a tiny bit brighter than neutral.

This is due to the treble, which has a peak just around 5 kHz that gives voices presence, which might be too much for some. However, this falls within an absolutely tolerable range for me. I like the gained effervescence and also the created airiness. Since the treble does not veil very much, the music should be mixed well, otherwise it can quickly become a bit tinny with cymbals, for example, and the treble sounds more unclean than it is. As I said, however, this is then clearly a weakness of the music material, since the L4 is quite uncompromising in the high frequencies. It lacks a bit of extension and level in the overtones, but still the brilliance does not come up short and will leave if only absolute treble fanatics with a disillusioned look. Personally, I even find the treble to be the absolute strength of the L4, which basically also sets it apart from the L3 and gives it more added value.

Technically, the L4 is very solidly positioned and more than commensurate with its price tag. It creates a light out-of-head experience with very good separation and layering. Listening to music with the L4 is fun not only because of the good tonality and punchy foundation, but also because of fine details that are very easy to locate and always keep you entertained and interested. The 4 drivers harmonize with each other and can play to their respective strengths. Yes, you can hear that BA drivers are responsible for the midrange and treble, but not because this area sounds unnatural, but just the advantages of the driver type come to the fore.

Switch - the L4 is equipped with 2 dip switches on the housing. Similar to the L3, however, the first switch is practically useless and a sonic change requires some imagination.
The second switch, however, makes an audible difference and is a nice tool to modify the sound according to one's preferences. I personally favor the 0|1 setting, as it brings more balance to the signature. In the 0|0 setting, the L4 goes more in the "V" direction with more level in the bass and treble. For me, it then becomes slightly unpleasantly spiky and the mids recede a bit more into the background. Nevertheless, this setting can provide added value for rock music, for example.



For me, the Legacy 4 is an IEM that not only plays tonally on a very high level due to its, to say the least, balanced mainstream tuning with a slight brightness, but also doesn't have to be accused of much technically. Whoever decides to buy the L4 will also have a lot of fun with the IEM beyond the new-toy bonus, because in addition to its all-rounder qualities, it also brings the necessary pinch of sensitivity to make audiophile hearts beat faster.
The L4 is for me the symbol of the middle class with features of the upper class. Of course, you won't find absolute resolution, scalpel-sharp separation or excessive extension at both ends in the L4, but that would also be a (wishful) TOTL-IEM, which is much more expensive.
What must be credited to the L4, however, is the authentic, refreshing and natural playing style with fine details and level stability. Tonally without gross blunders, even if certainly not neutrally tuned and in addition an extremely long-term reliable IEM, which delivers an outstanding overall package and brings out the clear advantages of a hybrid IEM.

If you like it a bit more crisp and technical and want to focus more on neutrality instead of musicality, you should take a look at the SEEAUDIO YUME in the same price range, which is also an amazing value.

More reviews: CHI-FIEAR


A New $200 Benchmark
Pros: Great mids tuning
Tight DD bass
Unabashed treble
Great accessories and packaging
Awesome cable
Energetic signature
Cons: Tiny treble peak that some might find harsh

After the release of the Thieaudio Legacy 5 a few months ago, I could've sworn I saw a comment on the Linsoul Discord saying that there weren't any more plans for a new IEM from Thieaudio for a while. Well, here we are with the Legacy 4. At a $200 price point and a 1 DD + 3 BA driver setup, it lands right between the older Legacy 3 (1 DD + 2 BA) and the newer Legacy 5 (1 DD + 4 BA). What makes the L4 interesting is that it takes the concept of tuning switches from the L3 but builds off the design philosophies of the L5. It also introduces a new DD that's supposed to be an upgrade from the one found in the L5 and Monarch/Clairvoyance. Thus, the obvious question that immediately follows is: is the L4 better than the L5 for $50 cheaper? With that in mind, lets take a look at the Thieaudio Legacy 4.

Disclaimer: The Thieaudio Legacy 4 was provided to me by Linsoul in exchange for this honest review. I am not or will be compensated in any other way.

What's in the Box?

I must say, I am extremely impressed with package that the Thieaudio Legacy 4 comes in. You get a massive carrying case that holds the IEMs, tips, and IEM case. This case is made of rather decent material and does NOT feel cheap at all. You get 6 sets of generic S, M, L tips. The smaller rectangular IEM case is very similar to the larger overall case and houses a 2-pin cable. The inside of this IEM case even has a soft furry lining and a pillow-like bed. To be honest, I can't help but think that Thieaudio probably could've saved everyone like $10 with simpler packaging but hey, this unboxing experience was a welcome step up from your standard cardboard box.

The 2-pin stock cable that comes with the L4 has pre-molded ear hooks and is very good. Soft, pliable, light, little cable noise, little cable memory. Every cable should aspire to be at least of this quality. The fit and comfort of the L4 is excellent as well. The shell is small and very light. I get a tight seal that causes a little bit of DD crinkle upon insertion. There is a lack of a nozzle lip on the L4. Combined with the tight seal, sometimes ear tips get stuck in my ear when I try to remove the L4. It's a minor annoyance, but an annoyance nonetheless. Finally, there are two tuning switches on the L4 for a total of four tuning options. You will have to use a SIM ejector tool or similar as these switches aren't accessible otherwise.


My first impressions of the Legacy 4 were positive. As expected from the newer Thieaudio IEMs, the mids tuning is on point. The real difference maker is the new DD. Compared to the L5, the bass is much tighter and responsive. Coupled with a forward treble, the Legacy 4 sounds lively. From this standpoint, I think the L4 is differentiated from the L5 which has a more relaxed and laid-back signature. I find myself more inclined to listen to energetic tracks with the L4 than slower ballads.

Tuning Switches:

There are four total configurations for tuning the Legacy 4. I don't know why Thieaudio insists on using ON and KE as names for the switches. So I'll opt for a standard 00, 01, 10, 11 system.

Interestingly enough, the first (ON) switch ostensibly has no effect on the frequency response. I was pretty surprised by this as I was ABing the switch quite extensively before graphing and thought that it affected the bass by a little bit at the lowest registers. For me, when that switch is up (0 position), I felt that the bass right at the interface between subbass and midbass had a little more of a thump to it. By contrast, in the down position, the bass was cleaner and better defined. But looking at the graphs now and trying to AB it again, I feel like I can hear that difference but it's diminished enough that I'm starting to wonder if it was some sort of placebo effect in the first place. Ah, the wonders of psychoacoustics.

The second (KE) switch has a much more straightforward dip in the mids. Though it looks pretty significant on the graph, it's a lot less drastic in practice. The biggest deviation is about 2.5 dB in the mids at about 500 Hz. I'm a lot less sensitive to changes in this part of the audio spectrum compared to say, the upper mids and treble. Thus, this switch adds a noticeable but subtle mild V-shapedness to the L4. What's also interesting is that if you normalize the curves to the 1 kHz mark, they look extremely similar. But since I didn't change my volume between AB testing, the un-normalized curve is how I interpreted it.

I prefer it in the up position and will move forward with this review using the 10 setting. Just keep in mind these two points on the tuning switches if you want to translate my review to a different setting.


The bass of the L4 is reasonably elevated to provide a consistent bass presence without being overbearing. It extends nicely to give subbass rumble. But really, the L4 is more of a midbass IEM. It opts of a controlled presentation rather than a booming bass response. The bass quality in the L4 is a breath of fresh air from the slower, tired feeling DD of the L5. The driver is fast and punchy. It feels tight and raring to go. Resolution is solid with a nuance that isn't smoothed over like other DDs. Instruments are well defined and the L4 particularly shines with the bass guitar and kick. If I had to nitpick, I'd say I wish the bass had more impact and better texture. But given the price point and overall quality, the L4's bass is plenty enjoyable.


I'm not sure how the 1 DD + 3 BA is exactly configured on the L4, but I can say that I don't notice any oddities in the transition from the bass to the lower mids. It sounds natural and done cleanly without sloppiness. There's not much to say here other than it sounds great on my 10 setting. The mids tuning is comfortable and just feels right. There's a very good balance between instruments and vocal presence. Vocals never fight for space on the L4 and takes a clean center stage. Try as I might, I can't really think of anything to nitpick here.

But if you were on the 01 or 11 setting, the mids do change a little. It becomes thinner and less full. With instruments, I barely hear a difference. But with vocals, the lower harmonies sound a little sucked out. To be honest, it's pretty subtle and if I didn't actively AB test it to see which I preferred, I probably wouldn't have cared if I was just using the L4 casually for commute. At any rate, I strongly suggest that if you do get an L4 to try it for yourself and see which you prefer.


I really like the treble of the L4 but those treble sensitive should be a little wary. It's well elevated and doesn't try to smooth over or hide anything. However, there is a small peak right around the 5 kHz that can occasionally make music sound a little harsh, depending on how well the track is recorded anyway. Thankfully, I don't hear any vocal sibilance despite that peak. This bit of treble elevation does make the lower treble of the L4 sound crisp. As the rest of the region is similarly elevated, decay rings out naturally.

In fact, other than the slight brightness, I'd say the treble of the L4 represents a starting point of what a well tuned treble should look like. It passes my hats/cymbals tests rather easily and avoids a lot of the common pitfalls that IEMs have in the treble. It doesn't try to hide the lower treble nor does it have major dips and valleys that throw the timbre off. The only thing I'd say is lacking on the L4's treble is upper treble extension for air/sparkle but you only ever truly see that on a small subset of IEMs anyway.


I'd say that the soundstage and imaging of the L4 is on the good side of average. There's a bit of depth, not a lot a height, and decent horizontal width. Imaging is relatively nuanced within that stage. Layering is constrained due to a lack of perceived depth but separation isn't an issue thanks to how well defined instruments are with the L4. Resolution is solid for its price class. Altogether, the L4's technical performance here is what I would consider the benchmark for $200.

Now I will note is that the Legacy 4 does sound kinda compressed. But when I compared it to the L5 or other IEMs I had lying around, they performed at about the same level. I think it's less about the L4 being compressed but rather the fact that thanks to the L4's energetic tuning, it amplifies this limitation commonly found on IEMs.

Should You Buy It?

Yes. It's a very good IEM. As strange as this may sound, I think of the Thieaudio Legacy 4 as an upgraded version of the Tin HiFi T2 Plus. Beyond the technical improvements, the bass is fixed, the tonal balance of the mids are improved, and the L4 retains the brighter treble tuning. With the ~$100 price range being dominated by the Tin T4, Moondrop Starfield, and Etymotic ER2, it's nice to see an IEM that anchors the $200 price point. That said, if you're happy with the T4/Starfield/ER2, I wouldn't upgrade to the L4. It's better if you're coming for the budget $50 class of IEM like the aforementioned T2 Plus.

For the most part, I think you can safely skip the Legacy 3, save a bit more cash, and opt for the Legacy 4 instead. Whether or not you should get it over the Legacy 5 is a bit of a tricky question. I think for most people, the Legacy 4 should be the one you get. But if you specifically want a more laid-back tuning for listening to music as you work, the Legacy 5 remains the better option. I find the L4 to be a great commuter IEM but if I'm working, it's a bit too energetic for me.

Overall, the best thing I can say about the L4 is that I really did enjoy listening to it over the course of this review. I try to spend a couple of weeks listening to gear before I review them and sometimes it's a pain to listen when I'd rather spend my time with something better. With the L4, it was easy to reach for it and enjoy music. For now, at the $200 mark, I'm satisfied with the Thieaudio Legacy 4. I do have the Seeaudio Yume in my review queue, which is another $200 IEM that's been gaining some traction, so I look forward to seeing how that stacks up.

Written by Fc-Construct


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