Sound Impressions
The following sound impressions of the THIEAUDIO Monarch MKIV were completed using a mixture of my main source, Lotoo’s PAW Gold Touch, the Questyle CMA18P, and the Campfire Audio Relay dongle Dac/Amp.
For the review, I paired the IEMs with the stock cable and stock silicon ear tips, size L. Most of my listening was done on the STANDARD mode unless stated otherwise.
Summary
The Monarch MKIV carries a balanced yet highly refined sound that feels both technical and musical. It’s a tuning that grows on you quickly with its clean, open presentation, which feels effortlessly detailed without ever sounding sterile or fatiguing.
The bass hits deep and clean. There’s real depth here, that kind of sub-bass rumble that sits under the music instead of jumping at you. T
he midrange feels natural and smooth, with the right amount of warmth that gives vocals and instruments body. The small details come through naturally; you don’t have to go looking for them.
The treble is where the Monarch MKIV really shines. It’s smooth and airy, detailed but never sharp. There’s a nice shimmer up top that adds space and energy, and it does it without getting harsh.
On the technical front, the Monarch MKIV will impress you from the get-go. It has great separation, clean layering, and a stage that feels wide, open, and immersive.
The two tuning modes actually make sense, providing two distinct flavors. The STANDARD keeps things balanced and reference-like, while RUMBLE adds a bit more warmth and weight.
All said, the Monarch MKIV feels like THIEAUDIO refining what they already do well. It’s polished, musical, and easily performs like something that should cost more than it does.
Bass
The bass on the Monarch MKIV feels like the best version of THIEAUDIO’s IMPACT² system yet. The dual subwoofer setup has been around in the Hype series and earlier Monarchs, but this time it really comes alive.
I always felt that the previous Monarchs had the quantity right but missed a bit of that deep, visceral punch, the kind you can feel rather than just hear. The Monarch MKIV fixes that.
The low end digs deeper, hits harder, and feels more complete. There’s a proper sense of weight and rumble now, and it finally delivers that satisfying sub-bass presence I always wanted from this lineup.
What stands out most is how well-controlled it all is. The bass never spills into the midrange or muddies things up. It’s tight, textured, and quick on its feet.
You can tell the layering and separation have been tuned carefully, as you can easily pick the bass notes from different instruments, which come across cleanly without drowning or overlapping into each other.
The bass offers good punches when the track demands it, never goes too far forward, and doesn’t drown out the rest of the mix.
Switching over to RUMBLE mode adds about 3 dB of boost to the lows, and you can feel it instantly. The sub-bass thumps deeper, and the whole low end gains more body and warmth.
It’s not quite a “basshead” territory with brain-shaking bass, but it’s close enough to satisfy anyone craving a fuller foundation. The mid-bass gets a bit more punch, though everything remains in check, and the low end never bleeds into the midrange.
Overall, the Monarch MKIV nails the balance with its impactful and full-bodied bass. This low end has both muscle and finesse, easily the most mature low-end tuning in the Monarch line so far.
Midrange
The midrange on the Monarch MKIV keeps things very clean and honest. It’s got that typical THIEAUDIO balance: neutral, open, and clean.
In the STANDARD mode, the lower midrange leans on the lighter side, helped by a bass that stays in check and doesn’t creep up. That gives the midrange a lot of room to breathe. Vocals and instruments sound well-separated, and you can easily pick up the texture in voices or the small details in a guitar strum.
It’s a highly detailed tuning, but not cold or clinical. There’s still some warmth under the surface that keeps it grounded. The only thing I sometimes notice is that vocals could use a little more body, as they sit a bit lean, but the payoff is how clear and precise everything sounds.
Switching to RUMBLE mode changes things just enough to notice. The extra bass adds some weight to the lower midrange and fills out male vocals and instruments nicely.
You get a slightly different flavor where the edges are rounded off, the lower strings gain a gentle swell, and voices sit a notch closer to the ears.
After hours in the crisper STANDARD setting, coming back here feels refreshing as the song breathes easier, but with the same tiny details tapping on the window.
The upper midrange is handled really well. They bring in clarity and air but never feel harsh or shouty. Female vocals, strings, and pianos all have that nice sense of sparkle without getting fatiguing.
What I like most is how the details don’t jump out at you; they reveal themselves naturally as you listen. Nothing feels forced or veers into a sharp region.
The Monarch MKIV’s midrange sits right in that sweet spot between precision and musicality. It’s resolving but easy-going at the same time.
Treble
The treble on the Monarch MKIV is honestly what grabbed my attention first. It’s incredibly resolving, but not in that overly analytical way where everything feels dissected.
Notes come through clean, well-separated, and neatly layered, so you can catch every shimmer and micro-detail without ever feeling like the sound is being pushed at you.
What I really like is how controlled it all feels. There’s detail everywhere, but it’s delivered gently and never feels sharp or in-your-face.
It walks that fine line between precision and smoothness beautifully. Even though I find Monarch MKIV a very treble-forward IEM, it doesn’t sound peaky or exaggerated.
When switching to the RUMBLE mode, which adds more body and weight to the bass, the top end stays nearly untouched, just as lively and engaging as in the STANDARD mode. That consistency really shows how well the tuning has been done.
The EST drivers here might be the best I’ve heard in this price range. The treble is refined, detailed, and blends seamlessly with the rest of the frequency range. The Monarch MKIV handles busy, treble-heavy tracks with a kind of effortless calm.
The wide stage gives the highs enough room to stretch out and breathe, so nothing ever feels crowded or sharp. Even in songs packed with a lot of cymbal strikes or bright instruments, it keeps its composure. Where many IEMs would start to sound tiring, the Monarch MKIV stays smooth and easy on the ears.
Compared to the older Monarchs, this treble feels more mature. The earlier ones had a touch of sharpness or thinness up top.
The Monarch MKIV fixes that part, and everything is evenly polished and more refined. It’s treble done right: full of air, sparkle, and life, yet always in control.
Staging & Dynamics
The first thing that hit me with the Monarch MKIV was its enormous soundstage. It feels wide and immersive from the start. This is not stretched in a gimmicky or artificial way, but it is wide enough that you stop thinking about anything else as the level of immersion pulls you in.
Sounds spread out and extend past the ears, with a real sense of depth as well. Instruments don’t sit on top of each other. Instead, everything has its own pocket of space, which makes the whole presentation feel effortless.
Imaging is sharp, just as you’d expect. You can easily point out where things are coming from. Vocals are centered, drums sit slightly back, and little guitar licks hang off to the side.
It feels organized, never messy or cluttered, even on a fast-paced track. Complex passages are easy to follow, no matter how much is happening at once.
Treble plays a big role here. It is airy and open, giving the soundstage that extra lift, but never sharp or piercing. Pair the openness of the highs with the width of the stage, and you end up with instruments breathing freely.
Dynamics are strong and presented with ease. Finer details and shifts, like the fading ring of a cymbal, the texture of a quiet piano note, or the breathiness in vocals, all come through clearly.
When a song swells into a chorus, the jump in energy feels big and convincing. Both ends of the scale are handled smoothly. Resolution is also solid. You hear those hidden little layers in the background, but they never feel forced.
All of this adds up to an IEM that does a lot right. The Monarch MKIV is not just technically capable; it is enjoyable, balanced, and easy to listen to for hours.
Synergy
Efficiency
The Monarch MKIV has an impedance of 10Ω at 1 kHz and a sensitivity rating of 100 dB/Vrms. The IEM does not demand much power and can be comfortably driven by most sources, from small dongles to smartphones to smaller DAPs.
It can also take some extra power and shows a bit of scaling capability. With a few extra clicks of the volume wheel, it does not get too loud.
A powerful source can also improve the Monarch MKIV’s sound by making it a bit more expansive. On my Lotoo PAW Gold Touch, it takes more than 30 volume clicks to reach a comfortable listening level.
Since the Monarch MKIV stays quite neutral in its tuning, it also remains highly transparent to the type of sources you feed it.
I prefer a source leaning warm for the Monarch MKIV, as a very neutral or bright source can push the treble slightly forward and make the sound more incisive, which it does not need.
Source Pairings
The Monarch MKIV pairs nicely with most of the sources I tried, and two stand out for me: the Campfire Audio Relay dongle and the Lotoo PAW Gold Touch.
With the Relay, the match is better than I expected from such a small dongle. It brings a touch of warmth and a slightly analog character, which works really well with the Monarch’s neutral base.
There is also enough power behind it, so the Monarch MKIV doesn’t feel starved. Relay adds some body to the sub-bass, helping the bass land with a good impact.
The midrange comes across with a nice, musical tone, and the treble stays easy on the ears. You don’t get every little detail, but honestly, it doesn’t feel lacking. For a small portable source, it holds clarity well and adds a touch of warmth that makes it easy and fun to listen to.
Paired with the LPGT, the Monarch MKIV shows its real prowess. Even in STANDARD mode, the bass feels fuller and has more texture. The lower midrange carries more body, which makes vocals and instruments sound meatier and more natural.
Female vocals especially pick up some warmth, making them more engaging. The treble stays crisp and resolving with plenty of air and sparkle. The stage has good width, and it pushes deeper, so you get more layering and an improved sense of space.
On my other sources, like the Questyle CMA18P or the EarMen Angel, the treble occasionally feels like it is stepping outside the boundary and may sound a bit intrusive.
The CMA18P is otherwise very detailed and keeps the low end and midrange enjoyable, while the Angel can sometimes sound thinner and less full in the midrange. Both these sources offer plenty of power, helping the Monarch MKIV sound wide.
