The THIEAUDIO Monarch MKIII are premium in-ear monitors (IEMs) positioned just below the Prestige LTD flagship IEMs in the company's current lineup. THIEAUDIO claims their revamped design for the Monarch MKIII means these buds produce a punchier sub-bass and louder output with lower distortion than their predecessor, the THIEAUDIO Monarch MKII. But have these IEMs done enough to reign over your ear canals?
Our Verdict
The THIEAUDIO Monarch MK3 are mediocre for sports and fitness use. On the plus side, they do a good job blocking out mid-range sounds like people talking in the gym, and they don't leak much sound, so anyone working out near you won't be bothered by your audio. On the other hand, they don't have any controls, so adjusting your music mid-step isn't easy, and they don't have an IP rating against water or dust damage, so these would be a poor choice for an outdoor run. And then there's the cable. While it's detachable, it's heavy and can easily catch on something, which could result in damage to the cable, connectors, or buds.
- Leak very little audio.
- Stable fit.
- No controls on the buds or cable.
- No IP rating against water or dust damage.
The THIEAUDIO Monarch MK3 are a decent choice for commuting and travel. They don't have active noise cancelling and, therefore, do a poor job of blocking out bassier sounds like the rumble of a plane engine. That said, they can passively block out a good amount of mid-range sounds like commuter chit-chat. They also leak very little audio, so your audio won't bother anyone nearby. Their hard-shell carrying case is great for transporting the buds, but neither the buds nor the case have an IP rating, so be careful not to spill anything on them while in transit.
- Great mid- and treble-range noise isolation.
- Leak very little audio.
- No controls on the buds or cable.
- Poor at blocking out bass-range sounds like engine rumble.
The THIEAUDIO Monarch MK3 are sub-par for office use. They don't have an integrated microphone, so you'll need a standalone mic to take calls. Some might also find their in-ear fit a little uncomfortable for long days at the office. On the other hand, they do a good job blocking out mid- and treble-range sounds like office chatter and the whine of a nearby fan.
- Great mid- and treble-range noise isolation.
- Leak very little audio.
- No integrated microphone.
- No controls on the buds or cable.
- Poor at blocking out bass-range sounds like engine rumble.
The THIEAUDIO Monarch MK3 are wired-only headphones; you can't use them wirelessly.
The THIEAUDIO Monarch MK3 are mediocre all-in-one gaming headphones because they don't have a built-in mic, so you'll need to bring your own if you want to chat with fellow players. They're comfortable enough for shorter sessions, but since they're IEMs, they don't have the plush ear pads that traditional gaming headphones have. You probably won't want to wear these for marathon sessions. That said, these do an excellent job reproducing everything from explosions to dialogue, and their remarkably well-matched left and right drivers ensure you can accurately locate objects like footsteps in the stereo field.
- Remarkably consistent audio delivery.
- Stable fit.
- No integrated microphone.
- No controls on the buds or cable.
The THIEAUDIO Monarch MK3 have great audio reproduction accuracy. They barely deviate from their warm sound profile, reproduce transients clearly, and have remarkably well-matched left and right drivers, ensuring accurate reproduction of objects in the stereo field. They also reproduce your audio cleanly regardless of your listening level. As in-ears, they can't produce audio that interacts with your outer ear, so they don't sound like two angled monitors in an acoustically-treated room.
The THIEAUDIO Monarch MKIII have very good noise isolation performance, which is fairly noteworthy as they don't have active noise cancelling. Their passive isolation does a good job blocking out mid-range sounds like people talking, but you'll hear bassier sounds like a train's engine rumble.
The THIEAUDIO Monarch MKIII don't have a microphone, so you'll have to bring your own mic if you want to use them for phone calls. If that's your plan, these do a good job blocking out sounds like office chatter, so you can hear the person on the other end of the line.
The THIEAUDIO Monarch MK3 have fantastic frequency response consistency. As long as you seat them properly in your ears, you'll get consistent audio with every wear.
Performance Usages
Changelog
- Updated Jul 29, 2025:
We've updated the Sound Profile box with a link to a downloadable folder of EQ settings that will help you match these headphones' frequency response to different target curves available in our Graph Tool.
- Updated May 16, 2025:
This review has been updated to Test Bench 2.0, which adds the following tests: Stereo Mismatch, Group Delay, Cumulative Spectral Decay, PRTF, Harmonic Distortion, and Electrical Aspects. We've added new performance usages and updated the text throughout the Sound tests.
- Updated May 14, 2025: We've converted this review to Test Bench 2.0, which updates our sound tests and adds performance usages. You can read more about this in our changelog.
- Updated Mar 26, 2025:
We mentioned the Audio-Technica ATH-ADX3000 in the Passive Soundstage section of this review.
Check Price
Differences Between Sizes And Variants
The THIEAUDIO Monarch MK3 come in one variant, which has a black body and a black-and-white faceplate. However, if you're willing to pay a little more, you can order custom versions directly from the brand. Currently, they offer a total of six additional body colors and 14 faceplate styles for you to mix and match as you wish.
We expect our results to be valid for any of the customizable combinations on offer; see our model's label.
If you encounter another variant of these headphones, please let us know in the comments, and we'll update our review.
Popular Headphones Comparisons
The THIEAUDIO Monarch MKIII are premium in-ear monitors aimed at listeners who want portable high-fidelity audio reproduction. They share certain sonic characteristics with the MOONDROP x Crinacle DUSK, though the THIEAUDIO have a more detailed treble range. The MOONDROP x Crinacle come with a DSP cable, though, which gives you some scope for custom tuning. If you're looking for IEMs with a similar sound profile but can't stomach the THIEAUDIO's hefty price tag, the TRUTHEAR x Crinacle ZERO: RED are affordable IEMs that also have a warm sound.
If you want more high-quality sound headphones, check out our recommendations for the best audiophile headphones. You can also check out the best in-ear headphones and the best headphones for music.
The MOONDROP Blessing 3 and the THIEAUDIO Monarch MKIII are IEMs with slightly different sound profiles. The THIEAUDIO have a more elevated bass range that lends extra thump and punch to kick drums. They also have a slightly recessed treble, which either enhances their smooth sound or makes them feel a little dull, depending on your preferences. On the other hand, the MOONDROP are significantly cheaper and deliver a more balanced treble, which gives sounds like cymbals more shine than the THIEAUDIO manages. The MOONDROP are also a little lighter and apply less pressure within the ear canal, so some users will find them more comfortable.
The TRUTHEAR x Crinacle ZERO: RED and the THIEAUDIO Monarch MKIII have similar sound profiles but very different prices. If you like a balanced sound, either of these pairs will suit you well. That said, the THIEAUDIO leak less audio and do a better job blocking out external noise, but they are significantly more expensive. Whether the improvements are worth the cost is up to you.
The THIEAUDIO Monarch MKIII and the TRUTHEAR x Crinacle ZERO are targeted at different segments of the IEM market. The THIEAUDIO are much more expensive than the TRUTHEAR, but the two share a somewhat similar sound profile with a prominent bass response and balanced mids. That said, the THIEAUDIO's treble response skews the overall frequency response towards sounding warm, while the TRUTHEAR have a brighter treble response. If you're a bright trap triplet hi-hats fan, you might find the THIEAUDIO too dull.
The MOONDROP x Crinacle DUSK and the THIEAUDIO Monarch MKIII are premium IEMs targeted at users looking for the very best sound reproduction. Both pairs have fairly similar sound profiles, offering plenty of thump and rumble in the low end, though the THIEAUDIO offer a more present low-treble range, which can help make vocals sound a little clearer in dense mixes. But both pairs present instruments and vocals accurately. But the THIEAUDIO are significantly more expensive than the MOONDROP and lack the MOONDROP's DSP cable, which allows you to apply EQ presets to your audio.
Test Results
These headphones have a warm sound profile with a boosted bass, fairly flat mid-range, and gently rolled-off treble. The bass and mid-range are a little closer to the Harman IEM target curve than our own. Vocals and instruments alike are reproduced accurately, though fans of a brighter treble might prefer something like the TRUTHEAR x Crinacle ZERO.
If you'd like to tweak these headphones with EQ so they more closely match one of the target curves found on our Graph Tool, check out our downloadable folder of EQ settings.
These IEMs have outstanding frequency response consistency. Once you get a good fit and seal, these buds will deliver consistent audio with every wear.
These headphones have amazing bass compliance. The whole bass range response is slightly emphasized compared to our bass range target, resulting in thudding kicks and basslines that don't overwhelm the mix. In songs like Bitter Melon by Cola, each note of the prominent melodic bassline is clear, and individual pitches don't jump out of the mix unnaturally.
These headphones have excellent mid-range compliance with our target curve. The low-mids are virtually flat, but a small dip in the mid-mids can make instruments feel a touch distant. The high-mids are very slightly emphasized: vocals in songs like Send My Love (To Your New Lover) by Adele sound clear and detailed without being harsh.
The THIEAUDIO Monarch MK3 have fantastic treble compliance with our target. If you like a warmer sound, these are a good choice because the upper half of the treble range is gently rolled off. That said, some may find this sound makes cymbals sound dull.
The THIEAUDIO Monarch MK3 have excellent peaks and dips performance, meaning they generally hew closely to their warm sound profile. Most deviations are found in the treble range, where a small peak in the low treble can make the upper harmonics of a vocal sound a touch harsh, depending on the singer's pitch.
These IEMs have remarkably well-matched left and right drivers. There are virtually no differences in phase and amplitude between each driver, certainly none that you'd notice while listening to regular content.
These headphones have great group delay performance. The group delay falls beneath the audibility threshold, though it skirts the threshold in the bass region. You can generally expect tight bass and transparent transient reproduction from these IEMs.
These are in-ear headphones, so they can't produce audio that interacts with your outer ear. That means they're unable to create a passive soundstage that resembles listening to two angled reference monitors in an acoustically-treated room. If you're looking for similarly priced high-end over-ears with a solid soundstage, consider the Audio-Technica ATH-ADX3000.
These headphones have impressively low harmonic distortion. You'll get clean and pure audio reproduction regardless of your listening level.
These headphones don't require an amp to drive them.
These are the settings used to test these headphones. Our results are only valid when used in this configuration.
The THIEAUDIO Monarch MK3 are premium IEMs. The buds' bodies are made from premium resin. We tested the stock colorway version, which is mostly black apart from a swirly white pattern and some colorful, glittery highlights on the outer face of each bud. The THIEAUDIO brand name is printed on each bud in pale grey lettering. You can also order the buds with custom colors and faceplates directly from THIEAUDIO.
The contoured buds are designed to sit securely in each concha, supported by a copper-colored cable that wraps over your ears. Text on the inside of each bud helps you distinguish between the left and right one. They come with three sets of translucent white silicone ear tips and three sets of black foam tips that are color-coded by size.
These headphones have a decently comfortable fit. They come with small, medium, and large tips in both silicone and foam, so most people will have enough variety to find a fit and seal that works for them. However, if you've smaller ears, you might find that even the smallest tips are a bit painful. The outer part of the buds nuzzle easily and securely into your concha and distribute their own weight well. That said, they're quite heavy for IEMs, which may cause you some pain, and their heavy cable can create discomfort by pulling down on the buds.
Like most in-ears, these headphones are very portable. Still, they're a bit heavier than many other IEMs.
These headphones have a zip-up hard-shell case to store the buds and their accessories. The case is covered in a sturdy-feeling, thick fabric, and it'll do a good job protecting the buds from everyday damage like drops. It doesn't have an IP certification, so be careful not to pack the case next to anything that might leak liquid. The case is lined with softer material so that the buds don't get scratched. There's also a pouch on the inside, which helps keep the accessories organized, and an elastic band secures the buds in place.
The THIEAUDIO Monarch MK3 have a very good build quality. The bodies of the buds themselves are made from a high-quality resin that feels very robust, and the metal tips covering the speakers have a premium feel. Like many IEMs, the pins that connect the cable to the buds are very small and could get bent if not handled with care. Finally, the sturdy build quality of these headphones comes at the cost of added weight. The cable is heavy, and the buds weigh twice that of competitors like the MOONDROP Blessing 3.
These IEMs have a good, stable fit. They are designed to fit comfortably in your concha, and their cable then hooks over your ears, which helps keep them in place. Even heavy headbanging to your favorite Haken tune won't dislodge these from your ears. However, their cable is quite heavy, and if you move around a lot, the weight of it could cause them to become dislodged, breaking their seal with your ears. You'll also want to take care not to snag the cable on anything.
- THIEAUDIO Monarch MKIII headphones
- Detachable cable (47 in/1.2 m)
- 3x adapters (1/16 in/2.5 mm balanced, 1/8 in/3.5 mm single, and 11/64 in/4.4 mm balanced)
- 3x pairs of foam tips (S, M, L)
- 3x pairs of silicone tips (S, M, L)
- Hard-shell carrying case
- Microfiber rag
These headphones have great full-range noise isolation, which they accomplish purely via passive isolation. Since they don't have ANC, they don't do a great job of blocking out bass-range sounds like the rumble of a bus engine. However, they do a very good job of isolating you from mid-range sounds like chatty coworkers and excel at blocking out trebly sounds like fan whine.
These IEMs do a decent job of blocking out everyday sounds. They won't isolate you from the low-pitched rumble of a plane engine or a passing bus, but they'll greatly reduce the ambient sounds of an office, from your colleague's voice call to A/C whine. You also won't hear much in the way of pedestrian chit-chat when out on the street.
The leakage performance is remarkable. Even if you listen at loud volumes, audio that does escape is concentrated in the low- and mid-bass regions and will sound muffled to anyone nearby. Feel free to blast your favorite Sunn O))) tunes without fear of bothering people around you.
These IEMS come with a 47-in/1.2-m detachable cable. The smaller two-pin connectors plug into the buds, and the four-pin connector plugs into one of three adaptors: 1/16 in (2.5 mm) balanced, 1/8 in (3.5 mm) single, or 11/64 in (4.4 mm) balanced. You don't need a dedicated amp to drive these.
These buds don't have a built-in microphone, so if you connect them to your PC, you'll only receive audio.
You can plug these into your PlayStation controller's AUX port, but they can only receive audio as they don't have a microphone.
You can receive audio from your Xbox by plugging these into an AUX port. They don't have a mic, so you'll need to add one if you plan to chat while you game.
