Thieaudio Monarch MKIV In-Ear Headphones

The THIEAUDIO Monarch MKIV is a flagship hybrid IEM built for listeners who want high-end technical performance with more control over the final sound. As the successor to the Monarch MKIII, it keeps the multi-driver hybrid platform the Monarch line is known for, then adds one of the most useful upgrades in the category: an adjustable tuning switch that lets you move between a cleaner, more neutral presentation and a thicker, more bass-forward one.

With 2 dynamic drivers, 6 balanced armatures, and 2 electrostatic drivers, a T6 aircraft-grade aluminum shell, and a modular cable system with both 4.4 mm and 3.5 mm plugs, the Monarch MKIV is aimed at listeners who want resolution, separation, and flexibility in one package.

Why the THIEAUDIO Monarch MKIV Stands Out

• Adjustable tuning switch with STANDARD and RUMBLE modes
• Successor to the Monarch MKIII with more tuning flexibility
• 10-driver hybrid design with 2 DD, 6 BA, and 2 EST drivers
• Dual IMPACT2 dynamic drivers for strong sub-bass slam and texture
• T6 aircraft-grade aluminum shell for a more premium and durable build
• Latest modular cable system with both 4.4 mm balanced and 3.5 mm plugs included

More Flexible Than Most Flagship IEMs

The biggest draw here is simple: the Monarch MKIV gives you two distinct tunings in one IEM. That matters because a lot of premium in-ear monitors lock you into a single sound signature. The MKIV gives you a more reference-leaning option in STANDARD mode, then lets you move into a heavier, warmer, more physical presentation with RUMBLE mode.

If you listen across a wide range of genres, or you just do not want to rely on EQ every time you want more low-end weight, this is one of the Monarch MKIV’s biggest advantages. It is not just a spec-sheet feature. It changes how the IEM feels with your music.

Monarch MKIV vs Monarch MKIII

The biggest change from the THIEAUDIO Monarch MKIII to the Monarch MKIV is flexibility. The MKIII built its reputation on strong technical performance and a well-regarded tuning, but the MKIV adds a physical tuning switch that gives you two distinct sound profiles in one IEM.

In STANDARD mode, the Monarch MKIV leans back toward a cleaner, more studio-neutral balance. In RUMBLE mode, it adds more low-end weight and more low-mid body for a thicker, warmer, more powerful presentation. That makes the MKIV more versatile than the MKIII for listeners who move between genres or simply want more control over the sound without relying on EQ.

The MKIV also moves to a T6 aluminum alloy shell and includes THIEAUDIO’s updated Chocolate modular cable system. If you liked the MKIII but wanted more bass flexibility and a more premium physical build, the MKIV is the more adaptable version of the Monarch idea.

Standard vs Rumble Mode

STANDARD mode is the cleaner, more controlled setting. Bass stays deep and impactful, but the low-mid transition is tighter, which keeps the midrange clearer and more neutral. This is the better fit for listeners who want more separation, more vocal clarity, and a more disciplined overall balance.

RUMBLE mode adds 3 dB to the sub-bass shelf and lifts low-mid presence for more warmth, body, and slam. Bass guitars, kick drums, and the foundation of instruments come through with more weight. It is the more fun, more physical setting, and the one that will likely appeal most to listeners who want a stronger sense of impact.

Flagship Hybrid Design With Real Range

The Monarch MKIV uses a 2DD + 6BA + 2EST configuration with a passive 4-way crossover network, four independent sound tubes, and an impedance grounding network. That design is meant to give each driver group a clear job, with dynamic drivers handling low-end authority, balanced armatures covering the core of the mix, and electrostatic drivers extending the top end.

The low end comes from THIEAUDIO’s IMPACT2 system, which uses two 8 mm composite diaphragm dynamic drivers in an isobaric design. The goal is not just more bass, but better bass control, texture, and consistency. The result is a low end that can hit hard without turning the whole presentation soft or muddy.

Clarity, Width, and Strong Imaging

One of the reasons the Monarch MKIV has stayed relevant in the conversation is that it does more than just hit hard. It has a clear, open, technically capable presentation that makes small details easy to follow. It comes across as spacious and well organized, with the kind of stereo width and image placement that makes busy mixes easier to unpack.

That gives the Monarch MKIV a nice balance between engagement and precision. STANDARD mode leans more toward clarity and control, while RUMBLE adds weight and warmth without completely giving up the MKIV’s sense of openness.

Aluminum Shell and Better Hardware

The shell is made from T6 aircraft-grade aluminum alloy and CNC-machined for a more solid, premium feel than the resin shells many IEMs still use. Surface hardening also helps with scratch resistance and better protection against sweat and corrosion, which makes sense for an IEM that may see regular portable use.

THIEAUDIO also stepped up the hardware here. The tuning switch is easy to use, feels more robust than the flimsy switches found on some competing designs, and the included cable is a real upgrade rather than an afterthought.

Chocolate Modular Cable System

The Monarch MKIV includes the latest version of THIEAUDIO’s modular cable system, Chocolate. It uses thick 8-strand ultra-pure oxygen-free copper and silver-plated OFC wiring, and it ships with both 4.4 mm balanced and 3.5 mm unbalanced plugs in the box.

That means it is ready to work with a wide range of sources, from balanced DAPs and desktop headphone gear to more common single-ended outputs. It is one of those practical quality-of-life features that matters more in day-to-day use than it does on a spec sheet.

Who the THIEAUDIO Monarch MKIV Is For

The Monarch MKIV is a strong fit for listeners who want a premium IEM with real technical ability, meaningful bass performance, and more than one sound profile to work with. It makes sense for buyers who want strong imaging, good separation, and a clear step up in build over more conventional resin designs.

It is also a good choice for anyone cross-shopping other premium THIEAUDIO models and looking for a flexible all-rounder in the lineup. The Monarch MKIV may not be the most extreme option THIEAUDIO makes in any one direction, but that is also part of what makes it so easy to recommend.

Technical Specifications

What’s in the Box

• THIEAUDIO Monarch MKIV
• Upgrade cable
• 3 sets of ear tips
• Cable tie
• Cleaning cloth
• User manual
• After-sales service card
• Monarch MKIV stickers