The FiiO FT3 (350Ω) is 350Ω with a sensitivity of 100.4 dB/mW, which is 105.0 dB/V. To reach 100 dB SPL — genuinely loud, louder than most people listen — it needs 0.91 mW, or 0.56 V across the drivers.
That is a moderate load. Most USB dongles handle it without complaint; the weakest phone outputs will run out of volume before they run out of quality. 277 of 280 sources here have enough headroom. The cheapest portable source that does the job is the Apple USB-C dongle (US) at $9.
Sensitivity here is in dB per milliwatt. Why the unit matters.
FiiO publishes this as 105 dB/V (1 Vrms @ 1 kHz) — a figure per volt, not per milliwatt. At 350Ω the two differ by 4.6 dB, so the 100.4 dB/mW above is that published number converted, not a different measurement.
This is the conversion that online calculators skip. Quote the per-volt number as if it were per-milliwatt and this headphone looks 5 dB easier to drive than it is — which is roughly the difference between a dongle being enough and not being enough.
Source: fiio.com. How this data was built.
| As it is labelled | As printed | Tolerance | Standard |
|---|---|---|---|
| Frequency response | 7Hz-40kHz | not printed | not printed |
FiiO prints 7Hz-40kHz for the FiiO FT3 (350Ω), under the heading “Frequency response”. Source: fiio.com.
No tolerance is printed with it, so “7Hz-40kHz” says nothing about how loud this headphone actually is at 7 Hz.
Only what the maker printed; maker by maker.
| Level | What it is | Power | Voltage | Current |
|---|---|---|---|---|
| 85 dB SPL | quiet background listening | 0.03 mW | 0.10 V | 0.3 mA |
| 95 dB SPL | normal listening | 0.29 mW | 0.32 V | 0.9 mA |
| 100 dB SPL | loud listening | 0.91 mW | 0.56 V | 1.6 mA |
| 105 dB SPL | very loud | 2.9 mW | 1.00 V | 2.9 mA |
| 110 dB SPL | peaks on dynamic music | 9.1 mW | 1.79 V | 5.1 mA |
Most people listen between 75 and 85 dB; the 100 dB row leaves room for peaks.
The 15 cheapest of the 280 sources here that reach 100 dB SPL into 350Ω with at least 10 dB of headroom and no known hiss or output-impedance problem with these headphones. All 280 sources, judged for these headphones.
| Source | Type | Price | Power into 350Ω | Headroom | Verdict |
|---|---|---|---|---|---|
| FiiO KA11 | USB dongle | $29 | 19 mW | +13 dB | Comfortable |
| ddHiFi TC35AL | USB dongle | $46 | 19 mW | +13 dB | Comfortable |
| ddHiFi TC35Air | USB dongle | $46 | 19 mW | +13 dB | Comfortable |
| Fosi Audio N3 | Bluetooth receiver | $50 | 13 mW | +11 dB | Comfortable |
| iFi GO link | USB dongle | $59 | 12 mW | +11 dB | Comfortable |
| Tempotec Sonata BHD Pro | USB dongle | $60 | 26 mW | +14 dB | Comfortable |
| EPZ TP35 Pro | USB dongle | $70 | 10 mW | +10 dB | Comfortable |
| Tanchjim Space | USB dongle | $70 | 11 mW | +11 dB | Comfortable |
| Truthear SHIO | USB dongle | $70 | 11 mW | +11 dB | Comfortable |
| Aiyima A2 Pro | desktop DAC/amp | $75 | 14 mW | +12 dB | Comfortable |
| Moondrop Dawn Pro | USB dongle | $75 | 11 mW | +11 dB | Comfortable |
| FiiO KA3 | USB dongle | $79 | 12 mW | +11 dB | Comfortable |
| FiiO KA5 | USB dongle | $99 | 12 mW | +11 dB | Comfortable |
| HiBy FC4 | USB dongle | $99 | 10 mW | +10 dB | Comfortable |
| JDS Labs Atom+ (2nd gen) | desktop amplifier | $99 | 233 mW | +24 dB | Comfortable |
Hiss. At 105.0 dB/V these are sensitive enough to reveal a source's own noise floor. The noisiest source in the database, the Schiit Mjolnir 3, would put its hiss at roughly 13 dB SPL in these headphones — clearly audible in quiet passages. Check your own source.
Output impedance. At 350Ω these want a source output impedance below 43.75Ω to satisfy the one-eighth rule; 15 of the 192 sources that publish one miss it. Check yours here.
36Ω · 96.0 dB/mW · Easy
See requirements →32Ω · 98.0 dB/mW · Easy
See requirements →32Ω · 95.1 dB/mW · Easy
See requirements →32Ω · 90.0 dB/mW · Moderate
See requirements →62Ω · 92.9 dB/mW · Moderate
See requirements →62Ω · 92.9 dB/mW · Moderate
See requirements →Compared with its stablemates: vs FT1 · vs FT1 Pro · vs FT3 (32Ω) · vs FT5 · vs JT1.