Thieaudio Legacy 4 Review | Breakout

Thiaudio Legacy 4 review featured

In late 2019, Thieaudio released their first product, the Phantom full-size planar magnetic headphones. Since then they’ve produced several in-ear monitors which have received praise among the enthusiast community. In this review, I’m looking at the Thieaudio Legacy 4 earphones.

The Legacy 4 is a 4-driver hybrid IEM with 1 dynamic driver, 3 balanced armature drivers and 2-switch tuning system. It’s positioned in the middle ground of the entry-level L3 and the more expensive L5 models. After being thoroughly impressed with my custom L3, I was really excited to see what this new L4 would sound like. Read on to find out what happened.

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Disclaimer: This sample was provided for the purpose of an honest review. All observations and opinions here are my own based on my experience with the product.

Thieaudio Legacy 4

  • Hand-painted faceplates
  • Great build quality and comfort
  • Included accessories
  • Tight bass performance
  • Excellent resolution and detail retrieval

  • Some 3rd party eartips slip off easily due to short nozzle length
  • Treble might be fatiguing for some

Package and Accessories

From the moment you see the exterior box, you know that Thieaudio has taken significant strides in updating their packaging since the previous models. The Legacy 4 comes in a large black box with the brand and model names embossed on the top in white.

Gone is that horrible typeface that we saw on the Voyager 3 which has been replaced by one that looks many degrees more professional and premium. On the back of the box are a frequency response graph and specifications list.

Looking inside the box, there’s a large zipper carrying case with a fabric exterior. This contains the earpieces, 6 pairs of silicone tips (2 pairs each of S, M, L) seated on a thick aluminium slab. There’s also a smaller case which contains the detachable OCC cable. Finally, there’s a quick start guide and warranty card.


Hand-crafted and manufactured from imported German resin, the Thieaudio Legacy 4 shells have excellent build quality. Each faceplate has been hand-painted with black, orange and blue swirling design with a subtle glitter effect.

There’s a single vent on the front side, just below the 0.78mm 2-pin sockets which are flush on the surface. On the top side are the 2 tuning switches. The 3-bore nozzle has a small lip on it but due to the nozzle’s short length, I found that some eartips with wider cores tend to slip off occasionally.

Thieaudio Legacy 4 hand-painted faceplate

Internally, the Legacy 4 has an 8mm poly-membrane dynamic driver, a Knowles ED29689 BA driver and a customized Bellsing dual BA driver with a 3-way crossover. Just like the Legacy 3 model, the Legacy 4 also features a 2-switch tuning system that allows the listener to adjust the level of bass and midrange frequencies.

Thieaudio Legacy 4 tuning switches
Comfort & Noise Isolation

Legacy 4 is an exceptionally comfortable IEM. It’s vastly improved compared to the Voyager 3 body, at least according to my anatomy. The shells are quite small for a quad-driver hybrid model and they fit very much like a custom in-ear monitor as if they were made specifically for my ears.

The passive noise isolation is above average (Thieaudio claims up to -26dB). That means the Legacy 4 is ideal for commuting, noisy environments and even as a studio or stage monitor and you won’t be disturbed by external noise.

Included 4-core OCC cable

The included stock cable is a braided 4-core OCC variant. The 2-pin connector housings, Y-split and straight 3.5mm plug are all matching polished aluminium. There are some very flexible heat-shrink ear guides and also a transparent plastic cable cinch or chin slider. This cable handles beautifully. It’s soft and supple but feels durable. It drapes very nicely and has almost zero microphonics.

Legacy 4 with carrying case


Gear used for testing

The Thieaudio Legacy 4 has a neutral-bright sound with a light, spacious presentation. End to end extension, detail retrieval and clarity are superb. With its low impedance and moderate sensitivity, the Legacy 4 has fairly low power requirements, however, it does scale to some degree with a better source.

Thieaudio Legacy 4 frequency response graph
Thieaudio Legacy 4 frequency response.
Tuning Switches

The 2 tuning switches give the user a bit of added flexibility by letting them make some mild adjustments to the frequency response. As is often the case with IEM switches, some of them hardly seem to do anything. I found the 1st or left switch to make almost no discernible difference to the sound at all. The 2nd or right switch, however, brings the midrange forward, adding body and making the overall presentation more linear.

Thieaudio Legacy 4 switches graph
Thieaudio Legacy 4 00/switches down (red) vs 11/switches up (grey).

Bass quantity from the 8mm dynamic driver is reserved but the control and definition are excellent. The Legacy 4 has confidence and surefootedness here and the bass is elastic and readily adjusts to each recording appropriately. Attack and decay speeds are fast, giving the L4 an almost BA-like bass but with that added dynamic sense of power.

The focus is on the sub-bass with the mid-bass having less intensity. I wouldn’t call the L4 a basshead earphone but in songs like Aes Dana’s “Far & Off” L4 gets down and dirty. Here the Legacy 4 drops the bass notes like a boss with a physical impact I wasn’t expecting.


Midrange notes are just slightly on the warm side of neutral. The density is somewhat light, giving the mids a spacious and open feeling. Vocals are neutrally positioned and are neither too intimate nor distant. The upper mids are a little intense and may cause discomfort from the 3kHz peak, especially with the right switch on.

With the right switch in the off position, male vocals could use a bit more fullness but are exceptionally clear and articulate. However, with the switch on, voices gain extra body and thickness which in turn, makes them sound more natural. What really stands out about the Legacy 4’s midrange is the resolution and spatial separation. You can hear every nuance and subtle shift in the music.


The treble has spice and I think it’s this area that will make or break the Legacy 4 for most people (along with the 3kHz rise). Most of the emphasis is on the lower treble which gives it abundant presence without making it brittle.

I normally don’t pay much attention to the hi-hats in Outkast’s “Liberation” but they really stand out with the Legacy 4 and it’s something you’ll either love or hate. It comes from the 5kHz peak which adds clarity, definition and sharp percussion attack. It’s a precise treble that reveals lots of detail but it does make the overall tonality somewhat bright and adds sharpness.


The soundstage is wider than average but the depth is fairly standard. Imaging is reasonable but not standout at this price; The lean nature and light density of notes don’t convey the sense of depth too well. Resolution and detail retrieval are both fantastic, however, they come at the price of a brighter tonality.

L4 shells


Mangird MT4 ($199)
Legacy 4 vs Mangird MT4
Thieaudio Legacy 4 (red) vs Mangird MT4 (grey).

The Mangird MT4 has the same 1DD + 3BA config as the Legacy 4. It also has a similar sound signature but one that’s slightly more linear. The MT4 is even more skewed towards sub-bass but has a lighter mid-bass punch. Both IEMs have a fast and tight bass response but the MT4’s leading edge is more rounded.

In the midrange, the MT4 has more note density and body. It’s not as resolving as L4 but instruments and vocals have more fullness and warmth. MT4 has less intense upper mids and more organic, smooth vocals.

Another key difference between these two earphones is the treble. MT4 dips slightly in the lower mids but has more upper treble. This makes percussion and instrument upper registers less sharp but not as precise as the L4. The Mangird is an IEM that I could listen to all day without listening fatigue while the L4 forces me to take a time out every now and then.

FiiO FH3 ($129)
Legacy 4 vs FiiO FH3
Thieaudio Legacy 4 (red) vs FiiO FH3 (grey).

The FiiO FH3 is a triple-driver hybrid IEM. It has a more upfront delivery with more bass presence, forward mids and good treble extension. Sub-bass extension is crazy on the FH3 and it carries more weight and rumble than the L4. Mid-bass is more boosted too and has thicker notes with less slam but more impact.

FH3’s midrange is more forward, warmer and full-bodied. On bass-heavy tracks, the FH3 has less resolution in the mids, due to some bass bleed and thicker notes. It has less upper-midrange emphasis which makes it less glaring than the L4 plus the FH3 produces a more natural tone here.

FH3 has a more laid back lower treble but better upper treble extension. Crash cymbals have more density and the overall treble is warmer albeit with more sparkle and air.

Thieaudio Legacy 4 with eartips and DAP.


Thieaudio Legacy 4 is another strong release from this startup company. It has been a privilege to watch them mature over time and go from strength to strength. The packaging is a major leap forward for the Legacy 4 and solidifies its image as a legitimate brand in the portable audio space.

Furthermore, the build quality of the L4 is superb and the new designs look fantastic. It doesn’t quite set a new standard but it comes close enough to earn my recommendation. If you like a neutral-bright tonality and love to hear every minute nuance this should be on your hotlist.

  • 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

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3 years ago

How does it compare to L3 in term of tonality?

Gordon Shen
Gordon Shen
3 years ago
Reply to  David Becker

I will probably stick with the l3 then, how does it compare to nm2+, thank you so much!!

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