These $999 IEMs remain at the forefront.
Thieaudio is well-known; Linsoul’s in-house brand made its debut over six years ago and has since released several successful models. The Oracle MKII demonstrated their capabilities in the mid-range, which they expanded upon with the Prestige LTD, a premium model featuring a distinctive tuning.
However, it is the Monarch series that truly characterizes the brand; the Monarch MKIII was launched at the end of 2023, retailing for $999 on Linsoul Audio. Similar to the Fiio FX15, the Monarch MKIII employs a tribrid driver configuration, incorporating dual dynamic drivers, six Knowles balanced armature drivers, and two Sonion EST drivers in each shell. Pair that with Thieaudio’s signature sound, and the Monarch MKIII continues to be an exceptional choice in 2025.
Thieaudio clearly aimed to set apart every aspect of the Monarch MKIII, beginning with its design. The IEMs come in a standard resin shell, but for an extra $100, you can extensively customize the design. There are six shell colors and 14 faceplate options available, offering a level of customizability that is uncommon among other IEMs in this segment.
The main drawback of opting for a customized design is the waiting period, which can range from two weeks to a month to receive the product, but this is reasonable considering you gain a unique look. I opted for the standard version, and although it doesn’t stand out as prominently as the custom colors, it still has an appealing appearance.
The shell is constructed from resin, and it features the usual stainless steel sound tube. The build quality is superb, and I encountered no issues during the month I used the Monarch MKIII. The fit is also quite good, although the IEM may be on the larger side, which could present challenges for those with smaller ears. Nonetheless, its contoured design ensures it remains securely in place when worn.
The Monarch MKIII comes with a set of foam and silicone ear tips, which are similar to those provided with other Thieaudio IEMs, which is a slight disappointment. Fiio excels in this aspect, as the high-end FX15 includes double the number of accessories.
Nonetheless, you should achieve a satisfactory fit with the included options, and Thieaudio’s included cable is of commendable quality. It connects to the earbuds using a standard 2-pin connector and features an interchangeable plug at the opposite end that allows for easy switching between 2.5mm, 3.5mm, and 4.4mm.
I appreciate the case that Thieaudio supplies with its products; it has a robust design and effectively protects the IEMs and cable. The packaging itself is appropriately upscale, and Thieaudio did well in this aspect.
The highlight of the Monarch MKIII is its sound; Thieaudio deserves acknowledgment for crafting a vibrant sound that excels across many genres. After using the Prestige LTD for nearly a year, I was thrilled with the low-end extension on the Monarch MKIII; it performs significantly better in this regard and provides a clear rumble.
Both sub-bass and mid-bass frequencies exhibit impressive vibrancy and energy, allowing for greater clarity. The mid-range features clean articulation, with vocals particularly standing out. Instrument separation is commendable as well, and ensemble music—such as orchestral pieces—sounds exceptional on these IEMs.
Treble offers good extension, and I did not notice any sibilance at any point. Thieaudio executed superbly with the dynamics and soundstage, and the Monarch MKIII possesses a sense of airiness and warmth that enhances the enjoyment of listening to music. Unlike many IEMs in this category, it is particularly adept at handling metal and thrashcore.
They also require very little power to drive, and I used them with the Fiio K19 and the M15S audio player. Overall, the Monarch MKIII fully earns its position in this category, and I was pleasantly surprised by how much I enjoyed using the IEMs. If you are in search of high-end IEMs with customizable design and revolutionary sound, the Monarch MKIII is an obvious recommendation.
