Short answer: a tie on sound quality. Both are rated 4.1/5 (#66 and #73 of 481 over-ear headphones) at nearly the same price ($219.99 vs $219.95), so choose on features and fit.
Why pick the FiiO FT3: The FT3 scores 85 for preference in the median of five hobbyist measurements on squig.link, with a 1.71 dB deviation from target and a warm tilt. The catch: At 350 ohms it needs a dedicated headphone amplifier to reach full volume and control.
What the Sennheiser HD 6XX does well: Measured response gives it an excellent Harman preference score of 84 with a 2.10 dB spread, and its mids sit within about 0.5 dB of target, so vocals and instruments sound natural. The catch: Sub-bass is 7.9 dB short at 30 Hz, so deep bass lacks rumble.
Buy the FiiO FT3 or the Sennheiser HD 6XX on features: they are rated the same for sound quality at close to the same price.
Still deciding? The full Headphones rankings cover every ranked option.
The FT3 scores 85 for preference in the median of five hobbyist measurements on squig.link, with a 1.71 dB deviation from target and a warm tilt.
Amazon $219.99 eBay
Measured response gives it an excellent Harman preference score of 84 with a 2.10 dB spread, and its mids sit within about 0.5 dB of target, so vocals and instruments sound natural.
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Specifications Side By Side
| FiiO FT3 | Sennheiser HD 6XX | |
|---|---|---|
| Price | $219.99 | $219.95 |
| Ranked | #66 of 481 in Over-Ear Headphones | #73 of 481 in Over-Ear Headphones |
| Form Factor | Over-ear | Over-ear |
| Harman Preference Score | 84 (median of 5 squig.link measurements, calibrated to AutoEQ) | 84 (measured by oratory1990, via AutoEQ) |
| Deviation From Target | 1.71 dB standard deviation | 2.10 dB standard deviation |
| Tonal Tilt | -0.47 (negative is warmer, positive brighter) | -0.27 (negative is warmer, positive brighter) |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-2.0 dB at 30 Hz) | Falls 6 dB below target at 40 Hz (-7.9 dB at 30 Hz) |
| Connection | Wired | Wired |
| Back | Open | Open |
| Driver Type | Dynamic | Dynamic |
| Drivers | 1 x 60mm dynamic | 1 x 42mm dynamic |
| Impedance | 350 ohms | 300 ohms |
| Sensitivity | 105 dB/Vrms | 103 dB/Vrms |
| Weight | 0.9 lbs (391 g) | 0.6 lbs (260g) |
| Frequency Response | 7Hz - 40kHz (Manufacturer specified) | 10Hz - 41kHz |
| Built-in Microphone | No | - |
Frequency Response Compared
Both headphones’ measurements overlaid on the Harman target. Above the target sounds louder in that range, below it quieter. Each curve is the median of several independent measurements, shifted so its 500 Hz to 2 kHz average sits at 0 dB, so only the tuning is compared.
Measurement data: the FiiO FT3 from daemonxar, gadgetrytech, kuulokenurkka, sai and vsg; the Sennheiser HD 6XX from audioamigo, daemonxar, gadgetrytech, hadoe, kuulokenurkka, ragnarok, sai and superreview, all via squig.link.
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