The same headphone is often sold in two or three impedances — 32, 80, 250, 600Ω — and the forums will tell you the high-ohm one “needs a proper amp”. That is only half true, and the half that is missing is the important one.
Beyerdynamic quotes the same 96 dB sensitivity for every impedance version of the DT 880 and DT 990, without ever printing whether that is per milliwatt or per volt. If it is per milliwatt — and one number spanning 32 to 600 ohms is a good reason to think so — then all three versions need identical power to reach the same loudness. What changes is how that power is delivered: the 600Ω version needs a lot of volts and hardly any current, the 32Ω version needs the opposite.
So the question is never “can my source make enough power”. It is “can my source swing enough volts” for the high-impedance version, or “can it supply enough current” for the low-impedance one. A phone runs out of volts long before it runs out of anything else, which is exactly why 600Ω headphones have their reputation.
There is a second, quieter reason to prefer the higher-impedance version if your source can drive it: audible hiss scales with sensitivity in dB/V, and a 600Ω headphone has a much lower dB/V figure than the 32Ω one. Same headphone, far less noise from the same amplifier. The trade runs the other way too — low impedance is more vulnerable to source output impedance.
The stubborn myth this page exists to kill is “more ohms means harder to drive”. Ohms and difficulty are two different axes. A 600Ω DT 990 is easier to drive than a 60Ω HiFiMAN Susvara by a wide margin, and the comparison tool will show you that in one screen.
There are 5 of them in this database, 13 models in total. The interesting column is the last one.
| Family | Versions in this database | What the maker prints | Per version? |
|---|---|---|---|
| Beyerdynamic DT 770 Pro | 32Ω, 80Ω, 250Ω | 96 dB | one figure for all |
| Beyerdynamic DT 880 Edition | 32Ω, 250Ω, 600Ω | 96 dB | one figure for all |
| Beyerdynamic DT 990 Edition | 32Ω, 250Ω, 600Ω | 96 dB | one figure for all |
| Beyerdynamic DT 990 Pro | 80Ω, 250Ω | 96 dB | one figure for all |
| FiiO FT3 | 32Ω, 350Ω | 110 dB/V / 105 dB/V | one per version |
Beyerdynamic prints one sensitivity figure covering every impedance version of a model, on a single line of a single table, and never prints the reference it belongs to. That shared number is not sloppiness: efficiency per milliwatt is roughly what stays constant when a maker rewinds the same driver, while a per-volt figure would move by about nine decibels between 32 and 250Ω. So one number across the versions effectively rules out the per-volt reading — it just does not say so, which is why these pages show both readings.
The FiiO FT3 is the exception, and it settles the argument on the maker's own numbers. FiiO publishes per volt for both, and per volt the high-impedance version looks less sensitive — which is exactly what people mean when they say it is harder to drive. Convert both to per milliwatt and the ranking flips.
| Version | Impedance | Maker prints | Per milliwatt | Power for 100 dB | Volts | Current |
|---|---|---|---|---|---|---|
| FiiO FT3 (32Ω) | 32Ω | 110 dB/V | 95.1 dB/mW | 3.1 mW | 0.31 V | 9.8 mA |
| FiiO FT3 (350Ω) | 350Ω | 105 dB/V | 100.4 dB/mW | 0.91 mW | 0.56 V | 1.6 mA |
Read the last three columns across, not down. The 350Ω version needs less power than the 32Ω one and roughly 1.8× the voltage at 6.1× less current. That is the whole point of this page: impedance moves the work from current to voltage, and a source runs out of one or the other long before it runs out of watts. A phone runs out of volts.
FiiO does not say whether these are the same driver rewound or two different ones, so this is evidence about what the maker publishes rather than about coil windings. It is still the only family here where you can read the answer off one maker's own spec sheets.