Overview

The FiiO FT5 is the company’s flagship open-back planar magnetic headphone. It features a large 90 mm driver with an ultra-thin ~6 µm PAR diaphragm, an array of 20 N52 neodymium magnets per driver with up to 1.5 T magnetic flux, and magnesium–aluminum alloy construction. Sensitivity is specified at 110 dB/1 Vrms (≈96 dB/mW) with 36 Ω impedance [2][3]. The tuning targets a warm, U-shaped presentation suited to relaxed long listening rather than strict neutrality.

Scientific Validity

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Third-party B&K 5128 measurements show controlled response with excellent channel matching, but a tonal balance with elevated mid-bass and some upper-treble energy deviates from neutral [1]. Manufacturer specs list 7 Hz–40 kHz bandwidth, 36 Ω impedance, and high sensitivity (110 dB/1 Vrms; 96 dB/mW) [2][3], consistent with easy drivability claims. Distortion performance is typical of modern planar designs per third-party comments, though comprehensive distortion datasets across SPL/frequency are still limited [1]. Overall fidelity is solid for the class, with intentional coloration limiting the score.

Technology Level

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The FT5 employs a contemporary planar architecture: 90 mm diaphragm, micron-level (~6 µm) PAR film, and a dual-side N52 magnet array (11 inner/9 outer) reaching up to 1.5 T [2]. Build uses a magnesium–aluminum alloy frame and dual 3.5 mm cup connectors with a rich accessory kit [2][3]. While competent and well-executed, these choices follow established best practices rather than introducing novel transducer breakthroughs.

Cost-Performance

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Current market price (review target): 499.99 USD [3].
Comparator (cheapest equivalent-or-better): HiFiMAN HE400se, an open-back planar with comparable user-facing functionality and adequate measured performance (see RTINGS) at 109 USD from the official store [4][5].
Reason for equivalence (minimum statement): Open-back planar magnetic headphone; frequency-response behavior and core specs (impedance/sensitivity class) are equivalent-or-better for general listening [4].

CP calculation: 109 USD ÷ 499.99 USD = 0.218 → 0.2 (rounded to one decimal).

Reliability & Support

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The magnesium–aluminum chassis and simple planar driver topology suggest robust mechanics. Weight is specified at 456 g; dual 3.5 mm cup connectors and included plug options reduce single-point failures [3]. As a passive design, there is no firmware risk. Long-term field reliability data specific to FT5 remains limited.

Rationality of Design Philosophy

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Engineering choices (large planar diaphragm, strong magnet array, rigid lightweight frame) are rational for durability and efficiency. However, prioritizing a warm U-shaped tonality over neutrality trades measurable transparency for a specific voicing. Emphasis on premium materials and accessories is sensible, but not directly tied to fidelity gains; hence a moderate score.

Advice

Choose the FT5 if you value a warm, relaxed planar presentation, premium build, and a generous accessory kit. Cost-focused or measurement-first buyers should start with cheaper planars like the HE400se, which deliver comparable core functionality at a fraction of the price. If you require neutral tuning, consider alternatives or EQ.

References

[1] The HEADPHONE Community, “Fiio FT5 Measurements & Official Discussion” (B&K 5128 graphs and notes), https://forum.headphones.com/t/fiio-ft5-measurements-official-discussion/23085, accessed 2025-08-26.
[2] FiiO, “90mm Open Planar Magnetic Headphones FT5” (official product page/specs), https://www.fiio.com/ft5, accessed 2025-08-26.
[3] B&H, “FiiO FT5 Over-Ear Open-Back Planar Magnetic Headphones” (price/specs incl. 456 g, 36 Ω, 110 dB), https://www.bhphotovideo.com/c/product/1818065-REG/fiio_ft5_open_back_90mm_planar.html, accessed 2025-08-26.
[4] RTINGS, “HiFiMAN HE400se Headphones Review” (measurement context), https://www.rtings.com/headphones/reviews/hifiman/he400se, accessed 2025-08-26.
[5] HiFiMAN Official Store, “HE400se” (current lowest price 109 USD), https://store.hifiman.com/index.php/he400se.html, accessed 2025-08-26.

(2025.8.27)