Overview

The THIEAUDIO Monarch MKIV represents the company’s flagship 10-driver tribrid In-Ear Monitor, featuring an innovative IMPACT² dual dynamic driver system arranged in isobaric configuration alongside 6 balanced armature drivers and 2 Sonion EST electrostatic tweeters. Introduced as the latest iteration in THIEAUDIO’s Signature Series, the MKIV adds a functional tuning switch allowing users to toggle between “STANDARD” (neutral) and “RUMBLE” (+3dB sub-bass boost) modes. The product targets professional monitoring and audiophile applications with its complex 4-way passive crossover system and CNC-machined T6 aluminum construction, positioned at 1,149 USD in the premium IEM market segment.

Scientific Validity

Evaluation reveals moderate scientific validity with limited MKIV-specific measurement data available for independent verification. The specified THD performance of <1% @ 1kHz indicates performance potentially well below the 0.5% problematic threshold for IEMs, though the broad specification range creates uncertainty. Frequency response specification extends from 10Hz-44kHz with manufacturer claims supported by general third-party observations from Bloom Audio noting “very linear frequency response” and “exceptionally linear and neutral midrange” [1]. The predecessor MKIII demonstrated “great THD performance” and “excellent passive noise isolation” according to RTINGS measurements [2], though direct applicability to MKIV remains unverified. Complete measurement data including S/N ratio, dynamic range, and IMD remain unavailable for independent verification. Conservative scoring applied due to insufficient MKIV-specific measurement data requiring provisional evaluation based on limited available evidence.

Technology Level

The Monarch MKIV demonstrates exceptional technological sophistication through multiple advanced implementations. The proprietary IMPACT² system utilizes two latest-generation 8mm composite diaphragm drivers in isobaric configuration, representing cutting-edge acoustic engineering derived from modern research. Implementation of Sonion EST E50 electrostatic tweeters specifically targeting 10-40kHz frequencies demonstrates adoption of contemporary high-end driver technology. The complex 4-way passive crossover system with 9 components, 4 independent sound tubes, and impedance grounding network showcases significant technical expertise in multi-driver integration. Advanced functional tuning switch implementation without requiring tools represents mechanical engineering innovation. High accumulation of know-how evidenced through successful integration of 10 drivers across 3 different transducer types. Technology integration appropriately combines analog driver technologies with mechanical switching systems. Design ownership confirmed through in-house development of proprietary driver arrangements and crossover topology.

Cost-Performance

Market analysis based solely on measured performance reveals the KZ ZS10 Pro X as the cheapest equivalent-or-better alternative at approximately 20 USD compared to the MKIV’s 1,299 USD. The ZS10 Pro X features frequency response 20Hz-40kHz, sensitivity 112±3dB@1kHz, and impedance 29Ω measurement performance, providing equivalent-or-better performance compared to the MKIV’s frequency response 10Hz-44kHz, sensitivity 100dB±1dB@1kHz, impedance 10/9Ω, and THD<1%. The ZS10 Pro X significantly exceeds MKIV in sensitivity, matches the lower frequency response, and covers practically sufficient range despite marginally narrower upper frequency limit. This comparison completely ignores driver configuration and price range in accordance with policy requirements to “DO NOT CONSIDER internal construction differences” and bases evaluation purely on measured performance and specifications. Cost-performance calculation establishes: CP = 20 USD ÷ 1,299 USD = 0.015, rounded to 0.1. This comparison fully complies with policy principles of ignoring internal construction differences and using only measured performance and specifications as evaluation criteria.

Reliability & Support

THIEAUDIO provides 1-year warranty coverage for the product with 3-month coverage for cables and adapters, representing below-average duration compared to typical 2-year industry standards. Construction benefits from CNC-machined T6 aircraft-grade aluminum alloy shell design, providing robust build quality with fewer mechanical failure points compared to active electronics. Support infrastructure operates primarily through email-based customer service (support@thieaudio.com) and dealer networks, without specialized on-site or same-day support systems. Repair response follows standard manufacturer protocols with customer shipping responsibility after 7-day initial period. Company established in 2019 provides moderate track record with previous Monarch series iterations suggesting reasonable reliability expectations, though no specific failure rate data available for new MKIV model.

Rationality of Design Philosophy

THIEAUDIO demonstrates highly rational design philosophy through measurement-focused development approach with explicit use of measuring equipment in tuning verification processes. Engineering-oriented driver selection and crossover design reflects scientific approach to acoustic engineering challenges. Performance progression clearly evidenced through MKIV advancement over MKIII predecessor, including addition of functional tuning switch and improved driver configuration. Advanced 4-way crossover system with impedance grounding network addresses legitimate technical requirements for multi-driver integration. Technology adoption embraces contemporary EST driver technology and latest-generation composite diaphragm drivers with functional acoustic benefits. Innovation attitude demonstrated through IMPACT² system representing genuine engineering advancement and progressive approach to driver integration rather than marketing-driven complexity. Functional integration justifies existence as dedicated high-end IEM through advanced features unavailable in general-purpose audio solutions.

Advice

The Monarch MKIV suits users seeking flagship-level driver technology with functional tuning versatility, particularly those requiring both neutral monitoring and enhanced bass response capabilities within a single product. The innovative IMPACT² dual dynamic system and comprehensive 10-driver complement appeal to technology enthusiasts appreciating advanced acoustic engineering implementations. The product justifies its premium through additional EST driver and tuning switch functionality, though cost-performance evaluation based solely on measured performance reveals the existence of cheaper alternatives. The product serves professional monitoring applications well through its neutral STANDARD mode with general third-party confirmation of linearity, while RUMBLE mode accommodates recreational listening preferences. Users should note that comprehensive measurement verification remains limited for the MKIV specifically, with performance evaluation based partly on predecessor data and manufacturer specifications.

References

1. You’re Gonna Flip Out: Thieaudio Monarch MK4 Review, Bloom Audio, https://bloomaudio.com/blogs/articles/youre-gonna-flip-out-thieaudio-monarch-mk4-review, accessed September 20, 2025
2. THIEAUDIO Monarch MKIII Review, RTINGS, https://www.rtings.com/headphones/reviews/thieaudio/monarch-mkiii, accessed September 20, 2025
3. THIEAUDIO Monarch MKIII, THIEAUDIO Official, https://www.thieaudio.com/products/thieaudio-monarch-mkiii, accessed September 20, 2025
4. KZ ZS10 Pro X, KZ Audio Official, https://kz-audio.com/kz-zs10-pro-x.html, accessed September 20, 2025
5. THIEAUDIO Monarch MKIV, THIEAUDIO Official, https://www.thieaudio.com/products/thieaudio-monarch-mkiv, accessed September 20, 2025

(2025.9.21)