Thieaudio Legacy 4: A New $200 Benchmark


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