THIEAUDIO Monarch MKIV Review — Headfonics

Nihal reviews the THIEAUDIO Monarch MKIV, a 4th-generation hybrid dual 8mm dynamic, 6 BA, and 2 EST driver universal IEM priced at $1149. 

Disclaimer: This is a sample in exchange for my honest opinion. Headfonics is an independent website with no affiliate links or status. I thank Linsoul and THIEAUDIO for this opportunity.

Click here to read more about THIEAUDIO products previously reviewed on Headfonics.

This article follows our latest scoring guidelines, which you can read in more detail here.

THIEAUDIO Monarch MKIV Review

Summary

The hybrid multi-driver THIEAUDIO Monarch MKIV IEM strikes a middle ground with its balanced sound. It’s detailed and technical but still musical and easy to listen to for hours. The treble is easily one of its strongest points, offering a lot of airiness and sparkle without being edgy.

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8.8

Pros

Two tuning modes offering versatility.

Deep, detailed and well-textured bass.

Highly detailed treble without much fatigue.

Cons

Large shells may cause fit issues.

THIEAUDIO has been on quite a ride lately. Back in December 2024, they dropped their flagship IEM, Valhalla, which gained significant popularity within the community.

In June, they followed up with a refreshed version of their acclaimed Monarch series. The last three releases in the Monarch lineup, namely the Monarch, Monarch MKII, and Monarch MKIII, have always been associated with an “endgame” experience at a relatively accessible price, serving enthusiasts well for the past few years.

My own ‘lightbulb moment’ came with the Monarch MKII, which I absolutely loved from the first listen. From that day on, I’ve kept a close eye on every new release the brand rolls out.

One notable aspect across the first three Monarch iterations has been their consistent pricing, which remained unchanged despite the upgrades.

With the new $1149 Monarch MKIV, however, THIEAUDIO has raised the price for the first time, marking a shift in positioning while still aiming to deliver the same benchmark “endgame” appeal that defined its predecessors.

In this review, I will dive into what the new iteration offers and how it compares with the Origin, BGVP’s Solomon, and the Moritz Audio ENZO.

Features

The THIEAUDIO Monarch MKIV has, at its heart, two dynamic drivers, six balanced armature drivers, and two electrostatic drivers.

Specifically, it has 2 ultra-high-frequency Sonion electrostatic drivers, 4 high-frequency Sonion balanced armature drivers, 2 midrange balanced armature drivers, and 2 dynamic drivers that handle the low-end frequencies.

The Monarach MKIV uses a 4-way crossover with four separate sound tubes to ensure the sound is well-separated and integrates smoothly.

For bass, the Monarch MKIV uses their IMPACT² technology seen in several of their hybrid IEM releases, including the Hype series and the Monarch MKIII.

This dual 10mm dynamic driver system, arranged in an isobaric chamber, acts as a true subwoofer for IEMs, delivering deep, controlled rumble in the bass frequencies, while the mids remain clear and unfazed.

A discreet toggle on the side of each shell gives you two tuning flavors: STANDARD mode keeps the low end polite and balanced, while RUMBLE mode lifts the low end by about 3 dB for a warmer, weightier feel that still leaves the mids unruffled.

Design

Breaking away from the resin shells used in all the earlier Monarch models, the Monarch MKIV adopts a metal shell design.

The Monarch MKIV is definitely on the bigger side, but the ergonomic shape makes it easier to live with. The shells have smooth curves and no sharp edges, which saves the day.

These are made from T6 aircraft-grade aluminum, which may sound heavy, but the weight is quite lightweight. The shells have a soft matte finish, and there’s some extra treatment done on the surface to help with scratches and mitigate corrosion due to sweat and humidity.

The faceplates are where things get exciting. I have with me the Kaleidoglow version, with a honeycomb pattern that shifts colors when light hits it. It has this subtle rainbow effect that looks lively without being flashy.

The other option, Stellashot, has vertical streaks that look like beams of light cutting across the faceplate. Honestly, I find both the designs appealing, making it harder to pick one over the other.

The good thing is that neither feels overdone, both feel tasteful with that soft iridescent shine. If you want something more personal, THIEAUDIO also lets you order custom faceplates for an extra charge.

The Monarch MKIV uses standard 0.78 mm 2-pin connectors and has a tuning switch on the side of each shell, letting you flip between two sound profiles. I couldn’t spot any obvious vents on the body, but there’s probably some internal design to handle built-up pressure.

The Monarch MKIV has large metallic nozzles, like most THIEAUDIO IEMs. The nozzles have lips for a better ear tip grip and are covered with mesh for extra protection from dirt.

Comfort & Isolation

The Monarch MKIV’s metal shells are lightweight, but the size is definitely on the larger side. I normally do not shrug off big shells, yet these still struck me as large when I first put them in my hands. The shells are nearly as large as those of Valhalla’s.

The good news is that the weight is balanced; they never feel like they are ready to tumble out of your ear, though they do sit sticking out more than average. If you have smaller ears, it’s worth trying them first to make sure the fit works.

Once you find the right ear tips, the shells sit comfortably. There are no sharp ridges or hot spots, so the shells simply melt into the concha, and the fit feels natural after a short while.

Even with some light movement, like turning your head or walking around, the shells stay put, and the weight doesn’t tug them loose.

The Monarch MKIV performs well at isolation, blocking out a fair amount of ambient noise. During my time with them, I didn’t encounter any driver flex or pressure build-up, which further added to the overall comfort of the experience.

In the end, the secure fit, smooth contours, and absence of weird pressure points make long listening sessions easy, provided the sheer size works with your personal anatomy.

Ear Tips

For what feels like time immemorial, I’ve been unboxing THIEAUDIO IEMs and finding the same ear-tip set: the iconic white silicone tips and a set of foam tips.

I’m now extremely disappointed to see the white ones gone, but we have two new and different silicone sets included. I call the white ones iconic because they’ve come with nearly every THIEAUDIO IEM I’ve reviewed, and unfortunately, they aren’t available for purchase separately.

Those white silicone tips have long been one of my go-to options. The only relief that works for me is the inclusion of an extra set of silicone ear tips with the Monarch MKIV.

The two new silicone sets, one with gray wings and blue stems, have wider bores, while the olive-colored set has a softer build and a narrower bore.

It’s nice that they cover a broader range of preferences and ear types. The gray set is closer in design to the earlier white ear tips and, thanks to the wider bore, sounds more open than the other set.

The foam tips have colorful stems for easy identification, but I didn’t bother trying them since I don’t get along well with foamies.

I also tried aftermarket options to see if anything paired well. Ultimately, the Divinus Velvet and AZLA SednaEarfit Light fit me fine.

Stock Cable

THIEAUDIO’s chocolate-brown cable is a thick and well-built cable that matches the Monarch MKIV’s premium feel.

If I am not wrong, this cable is the first eight-wire braided cable from THIEAUDIO, which uses ultra-pure oxygen-free copper combined with silver-plated OFC conductors that deliver low resistance and stable signal transfer, keeping the sonic picture clear and well defined.

The brown sheathing is smooth and malleable, so it naturally drapes around components, is never stiff, and does away with any microphonics.

The metal termination adapter is thick due to a slotted groove-like design, mixing grey and gold, similar to the adapter seen on stock cables on Valhalla and Origin. The modular system lets you quickly switch between 3.5 mm single-ended and 4.4 mm balanced terminations.

Every time you swap plugs, the satisfying click lets you know it’s locked in perfectly. The 0.78 mm 2-pin connectors at the top of the cable are housed in matching metal shells with the same gold accents and a grey body.

Although the cable takes up a bit of space and is generally thick across all elements, I never find it bothersome when using it, and compared with the rest of the THIEAUDIO IEMs, the cable on this one stands out for its quality construction and character.

Compared with Valhalla and Origin stock cables, this one is marginally thicker due to its eight-wire arrangement, yet it is easy to use.

Pair-wise, I find the cable has good synergy and believe users need not try different cables unless they have the itch to.

My only complaint with this cable is that it doesn’t match the IEMs’ color scheme and feels a bit lackluster due to its brown color scheme. I would have preferred a black cable with the same hardware.

Packaging & Accessories

THIEAUDIO takes a minimal approach to packaging, and they’ve been quite consistent with this style across their lineup.

From budget models to premium and flagship IEMs, the boxes all follow a similar format, with only the outer sleeve design differing to indicate which model is inside.

The Monarch IV follows the same trend. Its outer sleeve features a simple clipart-style illustration of the IEMs against a colorful abstract backdrop, along with details about the drivers and technologies used.

Inside, you’d be greeted with a clean and organized presentation. The carry case and IEMs, along with the cable, are neatly secured in foam cutouts.

Accessories include a cleaning cloth, a set of nozzle filters, two sets of ear tips, and termination adapters for the stock cable.

The internal layout mirrors what you’ll find with the Origin and Valhalla models. In fact, the carry case is identical, though the cable and ear tips are different this time, which is a welcome change for those used to seeing the same accessories bundled with most THIEAUDIO IEMs. A few Monarch MKIV stickers are also included, which you can paste on your laptop or gear.

Overall, the packaging feels appropriate for the price point, though a few IEMs in this range do offer a more elaborate unboxing experience.

Carry Case

The Monarch MKIV comes with a puck-style carry case handmade from eco-friendly Alcantara suede. By now, this case will be familiar, as it’s also included with models like the Origin and Valhalla. It has a soft, elegant feel, and the build quality is solid.

The round case opens with a sliding top that stays securely in place when closed, so it won’t pop open accidentally.

The interior is lined with a gentle cushion, offering some protection for the IEMs. The case has a small size, which makes it easy to carry and doesn’t take up much space.

However, as with many similar cases, the internal space is quite limited. It’s nearly impossible to fit both the IEMs and the cable inside comfortably; it feels suited for one or the other, but not both.

This has long been my complaint with such designs, and brands should really test by storing the IEMs themselves to ensure there’s adequate space.

Click on page 2 below for my sound impressions and recommended pairings.

Click on page 3 below for my selected comparisons.

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