Thieaudio’s Monarch series has become one of the most talked-about lines in the high-end IEM space, consistently appealing to listeners who want technical performance, premium design, and an engaging sound signature in one package. With the Monarch MKIV, Thieaudio continues to refine that formula, bringing a new 10-driver tribrid configuration, upgraded build elements, and a tuning approach that aims to balance audiophile precision with everyday musical enjoyment. For listeners looking at flagship in-ear monitors that can deliver detail, power, and long-session comfort, the Monarch MKIV arrives as one of Thieaudio’s most intriguing releases yet.
What You Get
- Thieaudio Monarch MKIV In-Ear Monitors
- New THIEAUDIO Upgrade Cable
- 3 Sets of THIEAUDIO Ear Tips (S/M/L)
- Cable Tie
- Cleaning Cloth
- User Manual & After-Sales Service Card
- Thank You Card
- 2x THIEAUDIO Monarch MKIV Stickers
Look & Feel
I love Thieaudio’s IEM designs, and the Monarch MKIV is up there with its best. There are a few versions you can get, the stellashot and kaleidoglow, as well as custom versions. The version I’m reviewing is the stellashot design, which is super elegant without looking too gaudy. The meteorite streaks are simple but effective at being aesthetically pleasing as a piece of audiophile bling. This is set on top of a durable aluminum shell with curves and bulges that represent an earphone with an ergonomic shape that should fit within the crevices of your ear. Some of ThieAudio’s IEMs can be quite big, but the MKIV is a good size that holds itself securely when worn without feeling too intrusive.
Design
The Thieaudio Monarch MKIV is built around a 10-driver configuration that combines dual 8mm dynamic drivers, six Sonion balanced armatures, and two electrostatic drivers. Its driver system is organized through a passive 4-way crossover with four independent sound tubes, separating low, mid, high, and ultra-high frequency reproduction for a more controlled presentation. The dual dynamic drivers use Thieaudio’s IMPACT2 isobaric subwoofer system for enhanced bass texture and pressure, while the balanced armatures handle midrange detail and treble clarity. The electrostatic tweeters extend the upper range for added air and high-frequency precision.
Soundstage
While some of the previous versions of the Monarch had more holographic soundstages that were more open, the MKIV reins everything in for better control and articulation. The MKIV solidifies the soundstage for more of a traditional stereo field, which makes it sound less like a bubble, but the level of accuracy is impressive enough to keep up the immersion. It’s a wide sound field that still retains its air, but the spatial imaging is more stern and front-facing.
Your preference for this soundstage depends on how much you favor a more studio-like sound over one that has a dome-like headspace. The MKIV is still capable of high levels of separation and articulate layering without having the greatest amount of dimension to it. Everything about the sonic environment the MKIV puts on display is incredibly engrossing, even when still linear, providing a good scale to the sound signature. Pan moves are slick, and layers of sound fold over each other with grace.
Low End
The Monarch MKIV supplies a special switch that will make or break what you think of its bass resposne. This “rumble mode” significantly increased the low-end power, featuring a tone with some of the smoothest vibrations I’ve heard in IEMs recently. The sub-bass dives super deep and rumbles with great definition, creating a pool of frequencies that form a rich timbre that grips you with its transparency. With rumble mode off, the bass still retains its clarity and detail, but the lift is taken out of the response.
While its surface is always very physical, the full shape of the bass is more complete with rumble mode switched on. It’s also just way more fun in a way that still feels like audiophile realism, while giving the listener something to bite on with just how effortlessly deep bass is articulated. It’s also a very tight response that has great ressonance but never bleeds outward. The MKIV keeps the lows in great balance even when dealing with a substantial sound.
Mids
If you’re worried about the mids stepping back to allow room for the lows, don’t be. The Monarch MKIV keeps up the weight of the sound signature with some very lively mids. Everything is brought up to an even level, with a clear tone that resolves beautifully for some stellar instrumental clarity. It’s like hearing the performances straight from the monitors as the band plays right in the studio. You get a great body to each note, and different sections are woven together with exceptional precision. Low-mids are buffed up a bit by the rumble switch, but the amount of warmth it gives you is subtle, leaning well away from cloudiness. Nothing gets left behind, and overall, the mids are very energetic while preserving a hyper-refined, organized tone.
Highs
The highs have exactly the right amount of air and clarity that makes for enjoyable treble. It’s a tone that appears consistently smooth, never resorting to extensive brightness or piercing textures. However, the highs are still very present, emanating with a coating of glimmer that allows for a perfect combination of coloration and realism. Like the rest of the sound signature, the treble has a very controlled resposne, but it still occupies a wide area with its heightened airiness.
Summary
The Thieaudio Monarch MKIV is a strong continuation of what has made the Monarch series such a staple among audiophile IEMs. Its design feels premium without being excessive, its fit is secure and approachable, and its sound brings together deep bass, lively mids, and refined treble with impressive control. The rumble mode switch is one of its biggest highlights, adding a more physical and enjoyable low-end response without sacrificing clarity or balance. While its soundstage may be more focused and studio-like than some listeners expect from past Monarch models, the MKIV makes up for it with excellent imaging, separation, and tonal organization.
For anyone looking for a high-end tribrid IEM that can sound immersive, clean, and exciting without becoming overly bright or bloated, the Monarch MKIV is an easy model to recommend. It captures the technical strengths Thieaudio is known for while adding enough personality to make it feel distinct in a crowded flagship IEM market.
The Thieaudio Monarch MKIV is available at Audio46 and Linsoul.
