The FiiO JM21 is a portable player at $199. It delivers 245 mW into 32Ω and 30 mW into 300Ω, which ranks it 93 of 156 for raw power among the sources in this database.
Measured at 100 dB SPL it has comfortable headroom on 386 of the 396 dynamic and planar headphones catalogued here and enough but not generous on 10. FiiO's budget sub-brand player, running Android. Note that FiiO publishes power for USB-DAC mode only — there is no rating for it working as a standalone player.
The manufacturer publishes 360 mW into 16Ω, 245 mW into 32Ω, 30 mW into 300Ω. Everything else in the table above is worked out from those figures, and this table says which is which.
The balanced output is rated separately: 700 mW into 32Ω through the 4.4mm jack.
Derivation holds output voltage steady between and beyond the published loads rather than output power, because that is what an amplifier actually does. The full method is written up here.
| Load | Power | Status | How it was arrived at |
|---|---|---|---|
| 16 Ω | 360 mW | Published | the manufacturer publishes this figure at this exact load |
| 32 Ω | 245 mW | Published | the manufacturer publishes this figure at this exact load |
| 150 Ω | 56 mW | Derived | worked out between two published loads, holding output voltage linear between them |
| 300 Ω | 30 mW | Published | the manufacturer publishes this figure at this exact load |
| 600 Ω | 15 mW | Derived | beyond the published loads, holding output voltage constant — which understates rather than flatters |
Ordered from easiest to hardest to drive. Headroom is measured at 100 dB SPL, which is louder than almost anyone listens — a small negative number means the source still plays loud, just without reserve for peaks.
These figures come from each manufacturer's own sensitivity rating. A handful of planars — the HiFiMAN Susvara and HE-6se and the Abyss AB-1266 in particular — are widely reported to need far more than their published sensitivity implies, so treat a bare pass on those as optimistic rather than settled.
| Headphone | Impedance | dB/mW | Needs | Headroom | Verdict |
|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 114.0 | 0.04 mW | +37 dB | Comfortable audible hiss |
| 64 Audio U12t | 13 Ω | 108.0 | 0.16 mW | +33 dB | Comfortable audible hiss |
| Shure SE215 | 17 Ω | 107.0 | 0.20 mW | +32 dB | Comfortable faint hiss |
| Moondrop Aria | 32 Ω | 107.1 | 0.19 mW | +31 dB | Comfortable faint hiss |
| Audeze LCD-X 2021 | 20 Ω | 103.0 | 0.50 mW | +28 dB | Comfortable faint hiss |
| Truthear Hexa | 21 Ω | 103.1 | 0.49 mW | +28 dB | Comfortable faint hiss |
| Sennheiser HD 25 (1-II) | 70 Ω | 108.0 | 0.16 mW | +29 dB | Comfortable faint hiss |
| Sennheiser IE 200 | 18 Ω | 101.6 | 0.69 mW | +27 dB | Comfortable faint hiss |
| Sony MDR-7506 | 63 Ω | 106.0 | 0.25 mW | +27 dB | Comfortable faint hiss |
| Meze 99 Classics | 32 Ω | 103.0 | 0.50 mW | +27 dB | Comfortable faint hiss |
| Focal Clear MG | 55 Ω | 104.0 | 0.40 mW | +26 dB | Comfortable faint hiss |
| Philips SHP9500 | 32 Ω | 101.0 | 0.79 mW | +25 dB | Comfortable faint hiss |
| Focal Utopia | 80 Ω | 104.0 | 0.40 mW | +24 dB | Comfortable |
| Meze Empyrean | 32 Ω | 100.0 | 1.0 mW | +24 dB | Comfortable |
| Campfire Audio Andromeda 2020 | 9 Ω | 94.0 | 4.0 mW | +17 dB | Comfortable |
| Etymotic ER2SE | 15 Ω | 96.0 | 2.5 mW | +21 dB | Comfortable |
| AKG K371 | 32 Ω | 99.1 | 1.2 mW | +23 dB | Comfortable |
| Audio-Technica ATH-M50X | 38 Ω | 99.0 | 1.3 mW | +22 dB | Comfortable |
| Beyerdynamic DT 900 Pro X | 48 Ω | 100.0 | 1.0 mW | +22 dB | Comfortable |
| Audeze LCD-2 Classic | 70 Ω | 101.0 | 0.79 mW | +22 dB | Comfortable |
| Grado SR80x | 38 Ω | 98.0 | 1.6 mW | +21 dB | Comfortable |
| Sennheiser HD 560S | 120 Ω | 100.8 | 0.83 mW | +19 dB | Comfortable |
| HiFiMAN Edition XS | 18 Ω | 92.0 | 6.3 mW | +17 dB | Comfortable |
| HiFiMAN Arya Stealth | 32 Ω | 94.0 | 4.0 mW | +18 dB | Comfortable |
| Dan Clark Audio AEON 2 Closed | 13 Ω | 90.0 | 10 mW | +15 dB | Comfortable |
| Audeze LCD-5 | 14 Ω | 90.0 | 10 mW | +15 dB | Comfortable |
| HiFiMAN Sundara | 37 Ω | 94.0 | 4.0 mW | +17 dB | Comfortable |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 102.0 | 0.63 mW | +17 dB | Comfortable |
| HiFiMAN HE400se | 25 Ω | 91.0 | 7.9 mW | +15 dB | Comfortable |
| Dan Clark Audio Stealth | 23 Ω | 90.0 | 10 mW | +15 dB | Comfortable |
| Fostex T50RP MK3 | 50 Ω | 92.0 | 6.3 mW | +14 dB | Comfortable |
| AKG K702 | 62 Ω | 92.9 | 5.1 mW | +14 dB | Comfortable |
| ZMF Verite Closed | 300 Ω | 99.0 | 1.3 mW | +14 dB | Comfortable |
| Sennheiser HD 650 | 300 Ω | 97.8 | 1.7 mW | +13 dB | Comfortable |
| Sennheiser HD 800S | 300 Ω | 96.8 | 2.1 mW | +12 dB | Comfortable |
| Beyerdynamic DT 770 Pro (250Ω) | 250 Ω | 96.0 | 2.5 mW | +11 dB | Comfortable |
| Audio-Technica ATH-R70X | 470 Ω | 98.0 | 1.6 mW | +11 dB | Comfortable |
| ZMF Atrium | 300 Ω | 96.0 | 2.5 mW | +11 dB | Comfortable |
| Abyss AB-1266 Phi TC | 50 Ω | 88.0 | 16 mW | +10 dB | Enough |
| Sennheiser HD 600 | 300 Ω | 91.8 | 6.6 mW | +7 dB | Enough |
| HiFiMAN Susvara | 60 Ω | 83.0 | 50 mW | +4 dB | Enough |
At 1.6 µV of output noise, here is where that noise lands in the five most revealing in-ears in the database.
This one hisses. With the most sensitive in-ears in the database its own noise lands around 19 dB SPL, which you will hear between tracks and in quiet passages.
| In-ear | Impedance | Sensitivity | Hiss level |
|---|---|---|---|
| Shure SE846 | 9 Ω | 134.5 dB/V | 19 dB SPL |
| 64 Audio Fourte | 10 Ω | 134.0 dB/V | 18 dB SPL |
| Shure SE535 | 36 Ω | 133.4 dB/V | 18 dB SPL |
| Shure AONIC 5 | 36 Ω | 133.4 dB/V | 18 dB SPL |
| Campfire Audio Andromeda 2023 | 6.375 Ω | 132.6 dB/V | 17 dB SPL |
At 1 Ω output impedance, the one-eighth rule says this source suits headphones of 8.0Ω and above. 8 of the 396 models here fall below that, mostly multi-driver in-ears, where the mismatch tilts the frequency response audibly rather than subtly.
The rule is a rule of thumb, not physics: a source impedance below one eighth of the headphone's keeps the interaction under about 1 dB. The checker works it out for any pair.
$350 · 18 mW into 32Ω · 1.5 Ω out
Compare →$479 · 140 mW into 32Ω · 1 Ω out
Compare →$480 · 262 mW into 32Ω · 0.6 Ω out
Compare →$499 · 200 mW into 32Ω · 1.5 Ω out
Compare →$649 · 250 mW into 32Ω · 0.5 Ω out
Compare →$699 · 125 mW into 32Ω · 1 Ω out
Compare →Or put any two side by side in the source comparison tool, or run your own headphones through the amplifier matcher.