Short answer: the ThieAudio Monarch MKIII. It ranks #1 of 297 in-ear headphones by sound quality, rated 4.9/5, at $999; the ThieAudio Monarch MKIV ranks #98, rated 4.4/5, and costs $1,149, so there is little reason to consider the other one.
The ThieAudio Monarch MKIII is the better-sounding choice. A preference score of 91 in HypetheSonics’ measurement, with an exceptionally smooth 0.77 dB standard deviation from target. Watch for: The air band from 10 to 16 kHz sits about 5.7 dB above target with a 4.4 dB peak near 11.9 kHz, which can add a hint of glare on bright or sibilant recordings.
Why pick the ThieAudio Monarch MKIV: Across 14 squig.link measurements it posts a preference score of 79.0 with a very smooth 1.31 dB spread. The tradeoff: Presence sits 2.7 dB below target with a 3.7 dB dip near 6.4 kHz, so vocals and strings lose some immediacy.
Buy the ThieAudio Monarch MKIII. It is rated higher for sound quality than the ThieAudio Monarch MKIV and costs less, so it is the default pick unless a specific strength of the other one matters more to you.
Still deciding? The full Headphones rankings cover every ranked option.
Specifications Side By Side
| ThieAudio Monarch MKIII | ThieAudio Monarch MKIV | |
|---|---|---|
| Price | $999.00 | $1,149.00 |
| Ranked | #1 of 297 in In-Ear Headphones | #98 of 297 in In-Ear Headphones |
| Form Factor | In-ear | In-ear |
| Back | Closed | Closed |
| Harman Preference Score | 91 (measured by HypetheSonics, via AutoEQ) | 79 (median of 14 squig.link measurements, calibrated to AutoEQ) |
| Deviation From Target | 0.77 dB standard deviation | 1.31 dB standard deviation |
| Tonal Tilt | -0.11 (negative is warmer, positive brighter) | -0.43 (negative is warmer, positive brighter) |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-0.8 dB at 30 Hz) | Within 6 dB of target down to 20 Hz (-0.2 dB at 30 Hz) |
| Connection | Wired | Wired |
| Driver Type | Hybrid (2 dynamic + 6 balanced armature + 2 electrostatic) | Hybrid (2 dynamic + 6 balanced armature + 2 electrostatic) |
| Drivers | 2 x 10mm dynamic + 6 x balanced armature + 2 x electrostatic | 2 x 8mm dynamic + 6 x balanced armature + 2 x electrostatic |
| Impedance | 18 ohms | - |
| Sensitivity | 99 dB @ 1kHz | 100 dB |
| Frequency Response | 20Hz - 80kHz (Manufacturer specified) | 10Hz - 44kHz (Manufacturer specified) |
| Built-in Microphone | No | No |
Related Headphone Comparisons
More worthwhile head-to-heads for ThieAudio Monarch MKIII:
- ThieAudio Monarch MKII vs ThieAudio Monarch MKIII
- ThieAudio Monarch MKII vs ThieAudio Monarch MKIV
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- Truthear x Crinacle Zero RED vs Tin HiFi T3 Plus
- Truthear x Crinacle Zero RED vs 7Hz Salnotes Zero
Prices on this page were last checked October 10, 2026 at 5:37 PM UTC. Product prices and availability are accurate as of that date/time and are subject to change; the price and availability shown on Amazon at the time of purchase will apply to the purchase of this product.
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The Two Headphones In Full
ThieAudio Monarch MKIII: $999.00 Linsoul eBay
Pros: A preference score of 91 in HypetheSonics’ measurement, with an exceptionally smooth 0.77 dB standard deviation from target. Everything from 20 Hz to 10 kHz stays within about 1.1 dB of target, so bass, vocals and treble all sound balanced and true. It rates above the pricier Symphonium Audio Helios and well above the SoftEars RSV.
Cons: The air band from 10 to 16 kHz sits about 5.7 dB above target with a 4.4 dB peak near 11.9 kHz, which can add a hint of glare on bright or sibilant recordings. It is a wired in-ear with no built-in microphone, so it is not suited to calls on the go.
Full ThieAudio Monarch MKIII review and specifications →
| Released | 2023 (3 years ago) |
|---|---|
| Back | Closed |
| Built-in Microphone | No |
| Connection | Wired |
| Deviation From Target | 0.77 dB standard deviation |
| Driver Type | Hybrid (2 dynamic + 6 balanced armature + 2 electrostatic) |
| Drivers | 2 x 10mm dynamic + 6 x balanced armature + 2 x electrostatic |
| Form Factor | In-ear |
| Frequency Response | 20Hz - 80kHz (Manufacturer specified) |
| Harman Preference Score | 91 (measured by HypetheSonics, via AutoEQ) |
| Impedance | 18 ohms |
| Sensitivity | 99 dB @ 1kHz |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-0.8 dB at 30 Hz) |
| Tonal Tilt | -0.11 (negative is warmer, positive brighter) |
EQ preset to match the Harman target
Set a preamp of -1.0 dB, then add these filters in any parametric equalizer (Wavelet, Equalizer APO, Peace, or a player with parametric EQ). Calculated by AutoEQ from its measured frequency response.
| Filter | Frequency | Gain | Q |
|---|---|---|---|
| Low shelf | 105 Hz | -0.1 dB | 0.70 |
| Peak | 742 Hz | +1.1 dB | 1.13 |
| Peak | 130 Hz | -1.1 dB | 1.51 |
| Peak | 1,584 Hz | -0.6 dB | 1.19 |
| Peak | 3,281 Hz | +0.9 dB | 4.08 |
| High shelf | 10,000 Hz | -7.9 dB | 0.70 |
| Peak | 8,077 Hz | +1.8 dB | 1.48 |
| Peak | 5,639 Hz | -1.4 dB | 6.00 |
| Peak | 9,669 Hz | +1.1 dB | 4.55 |
| Peak | 60 Hz | +0.1 dB | 2.11 |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
ThieAudio Monarch MKIV: $1,149.00 Linsoul eBay
Pros: Across 14 squig.link measurements it posts a preference score of 79.0 with a very smooth 1.31 dB spread. Sub-bass and bass sit within half a dB of target, so the dual 8 mm dynamic drivers give clean, accurate low end, and a 5 dB air lift near 12 kHz from the electrostatic tweeters adds shimmer and space. It rates above the SoftEars RSV.
Cons: Presence sits 2.7 dB below target with a 3.7 dB dip near 6.4 kHz, so vocals and strings lose some immediacy. The Moondrop Dark Saber rates well above it for less money, and the Symphonium Audio Helios rates higher at a similar price.
Full ThieAudio Monarch MKIV review and specifications →
| Released | Jul 2025 (1 year ago) |
|---|---|
| Back | Closed |
| Built-in Microphone | No |
| Connection | Wired |
| Deviation From Target | 1.31 dB standard deviation |
| Driver Type | Hybrid (2 dynamic + 6 balanced armature + 2 electrostatic) |
| Drivers | 2 x 8mm dynamic + 6 x balanced armature + 2 x electrostatic |
| Form Factor | In-ear |
| Frequency Response | 10Hz - 44kHz (Manufacturer specified) |
| Harman Preference Score | 79 (median of 14 squig.link measurements, calibrated to AutoEQ) |
| Sensitivity | 100 dB |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-0.2 dB at 30 Hz) |
| Tonal Tilt | -0.43 (negative is warmer, positive brighter) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons