Overview

ASHIDAVOX ST-31-02 represents a modern revival of the classic ST-31 studio monitor headphones used in recording studios from the 1980s to 1990s. Manufactured by ASHIDA SOUND CO., LTD. (founded in 1942), this model aims to bridge professional monitoring heritage with contemporary music listening. It features a specially designed 50 mm dynamic driver (film diaphragm), closed-back design, rated impedance 26 Ω, and sensitivity 104 dB/mW. Winner of the Entry Class Award at the Headphone Awards organized by Headphone Book 2024, it showcases Japanese manufacturing quality.

Scientific Validity

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Based on available third-party measurements [1], the ST-31-02 shows moderate technical performance. Impedance measures around 25 Ω with a main resonance at ~65 Hz, matching the 26 Ω spec; left–right channel matching is reported as excellent. THD rises in the sub-bass on the reviewer’s sample, while comprehensive independent datasets for THD/IMD vs SPL and frequency-response deviation (e.g., RMS error to a target) remain limited. Given partial but incomplete objective data, the scientific validity stays in a problematic-to-transparent band.

Technology Level

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The ST-31-02 employs a traditional dynamic driver with a film diaphragm rather than the original ST-31’s paper cone. The closed-back acoustic design and gold-plated plug are standard practices. No distinctive DSP or proprietary technologies that would confer a sustained advantage are evident.

Cost-Performance

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Per policy, we compare against the cheapest product with equal or better features and measured performance. A suitable floor reference is AKG K361 (closed-back, 50 mm). Independent tests report very low harmonic distortion (WHD 0.05 % @ 94 dB SPL, 0.13 % @ 104 dB SPL) and good target compliance (Bass profile RMS deviation 2.5 dB) [4]. Typical U.S. street price is USD 79.

79 USD ÷ 145 USD = 0.54

With an equal-or-better measured baseline available at roughly half the price, the ST-31-02’s cost-performance is below average.

Reliability & Support

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ASHIDA SOUND’s long operational history in professional audio inspires confidence. Official specs list approx. 250 g (without cable), indicating solid but not excessive mass; replacement ear pads are stocked (JPY 2,090) [2][3]. Global service coverage remains narrower than major multinationals, so overseas users should consider channel support before purchase.

Rationality of Design Philosophy

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The design continues proven studio-monitor principles while tuning for deeper bass and smoother highs. Investment went into a purpose-built 50 mm driver and resonance control rather than cosmetic features. However, the conservative approach limits innovation versus state-of-the-art materials or DSP.

Advice

Choose the ST-31-02 if you value Japanese craftsmanship and the classic studio-monitor lineage. If your priority is objective performance per dollar, options like AKG K361 deliver similar or better measured results at a meaningfully lower price. Regional availability and support should also be weighed for buyers outside Japan.

References

1. 0dB (YoungDB) measurement review (FR/impedance/THD commentary), https://www.0db.co.kr/REVIEW_0DB/3568210
2. ASHIDAVOX ST-31-02 product page (official specs/award/weight), https://ashidavox.com/items/628f058939da5f25d25f6c88
3. ST-31-02 replacement earpads (official), https://ashidavox.com/items/6321b6ca23c2aa7bdde17bdc
4. RTINGS — AKG K361 measurements (THD, target compliance, FR consistency), https://www.rtings.com/headphones/reviews/akg/k361
5. AKG K361 official page, https://www.akg.com/headphones/professional-headphones/K361-.html

(2025.9.4)