Thieaudio Monarch MKIV IEMs with Stellashot faceplate front center angled inward toward each other whitebox
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Thieaudio Monarch MKIV IEMs with Kaleidoglow faceplate front and side view of tuning switch whitebox
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Thieaudio Monarch MKIV | Flagship Tribrid Universal IEMs

Regular price$1,149.00
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Thieaudio new black logo

Take Control of Your Own Sound with Monarch MKIV, Thieaudio's First Signature Series IEM with an Adjustable Tuning Switch

  • (2x) Dynamic, (6x) Balanced Armature + (2x) Electrostatic drivers
  • Successor to the Thieaudio Monarch MKIII
  • Features adjustable tuning switch for versatile sound
  • T6 Aircraft grade aluminum alloy shell
  • Includes Thieaudio's latest modular cable system with 4.4mm + 3.5mm plugs

Thieaudio Monarch MK4 IEMs sitting on tier of black shelves with cable on the bottom, IEMs in the middle and iBasso DX260 MK2 on top shelf with vinyl record

Bloom's Take

Building on one of the most acclaimed tribrids in recent memory, the Thieaudio Monarch MKIV pushes the series forward with upgraded materials, greater versatility, and refined sonic performance. The Monarch MKIII was a massive hit for its balance of technical precision and musicality, and the MKIV answers the call for even more flexibility, comfort, and low-end authority without compromising the Monarch’s core identity.

Retaining its 10-driver tribrid foundation—dual dynamic drivers, six balanced armatures, and dual ESTs—the MKIV introduces a new CNC-milled aluminum shell for a sturdier, more premium feel. But the real innovation lies in the dual-mode tuning switch: Standard mode offers clean, detailed, reference-grade tuning, while Rumble mode engages a more muscular, bass-enhanced profile for added energy and low-end slam. The result is an IEM that can go from critical listening to guilty-pleasure bass tracks with a flick of a switch.

Visually striking and sonically adaptive, the Monarch MKIV represents Thieaudio’s most mature and well-rounded flagship to date. For those who loved the MKIII or are stepping into the Monarch line for the first time, the MKIV offers flagship-level performance with flexibility rarely seen at this level.

Read our full review.


Custom Tuning at Your Fingertips

Switch between studio-neutral and basshead tunings whenever you want. For the first time in Thieaudio’s Signature Series lineup, the Monarch MKIV comes with an adjustable tuning switch. Extensive R&D has led up to a functional tuning switch that is stylish, easy to use, and makes an extensive impact on the tuning.

Users can switch between “STANDARD” and “RUMBLE” modes. RUMBLE adds an additional 3dB to the entire sub-bass shelf, increasing both the sub-bass and low-mid power. With RUMBLE, the overall tuning profile becomes thicker, warmer, and more powerful. Monarch MKIV’s tuning switch allows users to enjoy both Monarch’s signature neutral tuning, while giving the option to experience the powerful bass slam like that of the Thieaudio Origin

T6 Aircraft Grade Aluminum Construction

The Monarch MKIV elevates its status by utilizing a premium T6 aluminum alloy shell. Precision CNC engineering achieves our most durable, yet lightweight, shell. Surface hardening also ensures more scratch resistance and corrosion resistance against sweat. Experience the fullness of your music with featherlight comfort in your ears.

All New Tuning Profile

The Monarch MKIV encompasses both tradition and modernity in its tuning profiles.

Standard Mode
In STANDARD tuning mode, the MKIV goes back to its roots by bringing back a studio-neutral tonal balance. The sub-bass dishes out a whopping 10dB of hard hitting bass, but with a sharp 150Hz low-mid cutoff, the bass is fast and precise, allowing for a clean midrange. The midrange has been cleaned up to be more neutral between 150Hz and 1kHz, while the treble is more crisp and natural. Compared to the previous generation, the MKIV’s treble focuses more on vocal clarity while eliminating unnecessary upper treble harmonics for a smoother and more candid treble extension.

Rumble Mode
In RUMBLE mode, the low-mid crossover is loosened, unleashing a more powerful bass and thicker mids. The sub-bass is boosted to 13dB to enable significantly greater thump and low-end presence. The low-mid range at 200Hz to 500Hz is also boosted by 2dB, giving greater body, depth, and texture to bass guitar, male vocals, and fundamental notes of instruments. RUMBLE is designed for those who love a thicker body in their music and want a more engaging bass.

Thieaudio Monarch MK4 IEM front view sitting on top of rack of vinyl records in a wooden box

IMPACT2

The IMPACT2 (“Impact Squared”) is Thieaudio’s tried and true subwoofer solution consisting of two latest generation of 8mm composite diaphragm drivers arranged in an isobaric design. The new 8mm dynamic driver focuses on speed and hard-hitting slam for a powerful, yet clean sub-bass thump. The usage of two 8mm subwoofers significantly enhances the power and texture of the bass, while our in-house isobaric chamber design keeps the frequency and pressure constant. This means you can enjoy better quality bass without sacrificing tonal integrity.

Electrostatic Tweeters

The Monarch MKIV completely redesigns EST driver utilization. By more efficiently targeting the treble range of its balanced armature tweeters, the Monarch MKIV can focus the EST tweeters specifically at the 10-40kHz region. This new crossover technique allows smoother treble transition between the BA and EST drivers for a more natural treble timbre, while simultaneously enhancing EST output into the ultra-treble range. The result is a greater treble extension compared to previous generations while sounding smoother and more natural. Enjoy the spacious soundstage, clarity, and air in the sound - more comfortably. 

Thieaudio Monarch MKIV IEMs sitting on silver vinyl record cleaner face out with AstellKern SP3000M DAP

Next Generation Modular Cable System

The Monarch MKIV comes with the latest iteration of Thieaudio’s modular cable system: Chocolate. Consisting of ultra pure oxygen-free copper (OFC) wires and silver plated OFC wires, enjoy cleaner and more fuller audio transmission. The modular plug design allows users to switch between 4.4mm balanced and 3.5mm unbalanced plugs for integration with any audio device. 

Specifications

  • Driver
    • (2x) IMPACT2 8mm Composite DD
    • (6x) BA
    • (1x) Sonion E50 EST + (1x) Sonion 28UAP
  • Crossover: 4-Way
  • Frequency Response: 10Hz-44kHz
  • Impedance: 10/9 ohms (±1 ohm) @1kHz
  • Sensitivity: 100dB ±1dB @1kHz
  • THD: <1% @1kHz
  • Thieaudio 1 Year Warranty

In the Box

  • Thieaudio Monarch MKIV
  • New upgrade cable
  • 3 Sets of ear tips
  • Cable tie
  • Cleaning cloth
  • User manual + After sales service card
  • Monarch MKIV stickers

Thieaudio Monarch MKIV IEMs in the box

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Customer Reviews

Based on 9 reviews
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A
Anonymous
A perfect all rounder IEM

The Thieaudio Monarch MKIV has earned a permanent spot as my daily driver. It’s one of those IEMs that just works with almost anything in my library — from jazz and acoustic to EDM with heavy drops. The balance is spot on, and when I want more low-end impact, it delivers with clean, controlled bass that never muddies the mids.

Vocals sound natural and clear, and the treble has enough sparkle to bring out detail without ever getting harsh. The soundstage feels open and well-layered, giving music a real sense of space without overdoing it. It’s the kind of tuning that keeps you coming back because it simply makes music enjoyable.

Build quality is excellent. The shells feel solid and well-finished, and the aluminum case is one of the nicest I’ve used — sturdy, good-looking, and actually practical. The stock cable is just as good, with a comfortable feel and no annoying tangles.

For me, the Monarch MKIV hits that sweet spot of versatility, great sound, and premium build. It’s not a “special occasion” IEM — it’s the one I reach for every day because I know it’ll make whatever I’m listening to sound its best.

A
Anonymous
Excellent all rounder - end game level

I loved the Monarch 3 but they were a little lacking in bass to me. Not by a lot, but enough to not be the set for me.

The Monarch Mark IV definitely solves that problem. I do also find the shells lighter and a better fit. While they do stick out a bit, and are on the large side, they feel better in my ears than the previous version. The b build quality is excellent, and the shells are gorgeous. I find the cable to be fine comfort wise, but the color is completely a mismatch with the actual IEM. If that's something you think about, keep it in mind. It wouldn't be a deal breaker for me, but I did use another cable with them. These do benefit from a balanced termination If you like higher volumes as they do need some power to shine up there.

Sound quality wise these are excellent across the spectrum. My goal is to find a warm and organic leaning set with a nice timbre, which still retains excellent technical performance. I find these fit that description to a t. Sometimes I do wish the mids were a slight bit more forward but it's rare. The bass switch is actually very functional and easy. You can simply reach up to your ears while you are listening and easily flick the switch. For example I was walking my dog and my playlist switched from beat driven music to some indie rock. I simply paused for a couple of seconds and turned the rumble off. Most switch implementations I've seen require you to remove the set from your ears and sometimes even have to use a small little tool. This implementation is much better.

If you have a varied music collection that works with this kind of sound signature, these are the all-rounders you want. These are not as specialist IEM, these are a throw anything at them, and you'll know it's going to sound good. If you want a specialist IEM for say acoustic music or just vocals, you could get a specialist set. If you're like me who listens to all kinds of different music from beat driven to classic Rock to jazz to electronic to indie rock, and
more, this is the set for you.

Highly recommended.

A
Anonymous
Great service from bloom audio

Received the monarch mk4 less than 24 hours after ordering them. Great service from bloom audio for making everything easy. Enjoy the personal touch as well that you don’t see from the big box stores.

J
Joseph B.
A True All-Rounder

Let me preface by saying: (skip this part if you don’t want to hear praise) Bloom’s customer service is phenomenal. Quick responses, all questions answered, and personal touches like candy, thank-you notes, and team cards make a big impression. It’s those small things that really set them apart—very happy with how Bloom handles things.

Now, the Monarch IV: a true all-rounder in genre versatility. The tuning and bass switch provide a gentle bump, adding warmth when certain genres call for it.

Packaging is excellent—6 pairs of silicone tips, 3 foam, a sturdy cable with a chocolate-like color. It doesn’t match the IEM’s look exactly but feels high quality, tangle-resistant, and includes 3.5mm and 4.4mm terminations. You also get a puck-style case that’s solid and satisfying to handle. However, fitting the IEMs inside can be tight—doable, but not without a bit of wrestling. If the case were slightly taller/wider, it’d be perfect.

The IEMs themselves feel premium and well-built. As for fit, they’re chonky. The nozzles and angles are okay, and once seated, they’re comfy and seal well—but people with smaller ears might struggle getting a flush fit due to the large shells.

Let’s head on over to where most people are even considering this: sound. These sound fantastic, review done.

Oh, not happy with that? I’ll elaborate. These as I said earlier, are a true real all rounder when it comes to music versatility, honestly anything I threw at it, sounded splendid. Really this can easily be yours and even my walkaway set if I started and done enough research to save and stop here, this set can really do it all with no sweat.

Bass – In reference mode, the bass is balanced with subtle punch. Notes are deep and textured. In RUMBLE mode, drops hit satisfyingly hard (rap, trap, EDM), and it doesn’t muddy the mids or treble—everything stays clean and crystal clear. If you’re a basshead, you may want more quantity, but the quality is top tier.

Mids – Beautifully clear and natural. No shoutiness, nothing hollow or recessed. Everything—from instruments to vocals—sounds just right.

Treble – Vibrant, airy, no sibilance or harshness. Nothing feels dark or fatiguing. The ESTs do excellent work here, rounding out the sound beautifully.

Thanks for reading my review—wish I could say more, but character limitations! Special thanks to Matthew for our order interaction and Steven for packaging this awesome product. Hope this helps your decision!

A
Anonymous
Versatile, well balanced.

3 week review (around 50 hours of listening time).
Gear: Samsung phone + Questyle M18i
Music: Korean ballads, EDM, Djent/Prog rock
Sound: Overall well balanced, enough detail and technicality to leave you not wanting more. Slightly too airy for my taste especially at high volumes (ended up EQing out anything >10kHz and some high mids). EQ's well. Staging adequate. Bass is textured. Would prefer different sets for pure vocals.

TLDR: Well-balanced versatile IEM that is easily EQ able. Rumble switch adds just enough bass for non-vocal-centric music.

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