The Warwick Acoustics Sonoma M1 is an electrostatic headphone. It does not connect to a normal headphone output at all — it needs a dedicated energiser that supplies a high bias voltage, so every power figure on the rest of this site is irrelevant to it. No dongle, amplifier or player will drive it, whatever its wattage.
That is the whole answer, and it is worth stating plainly because "how many milliwatts do I need" is the wrong question here. What you need is a matching energiser from the same ecosystem.
Electrostatic specifications are quoted differently and are not comparable to dynamic or planar headphones. They are listed here only so the database is complete.
Warwick Acoustics publishes no sensitivity figure for this model.
Source: warwickacoustics.com.
Warwick Acoustics prints no frequency range for the Warwick Acoustics Sonoma M1 at all. Source: warwickacoustics.com.
That is less unusual than it sounds, and arguably more honest than the alternative: of the 578 models checked so far, 490 carry a maker-printed range, and only 58 of those print the ±dB tolerance that would make the range mean anything.
What these numbers are worth, maker by maker, is set out in the frequency response audit. No measurement is published here — only what the maker printed.
200Ω · — · Moderate
See requirements →60Ω · — · Moderate
See requirements →200Ω · — · Moderate
See requirements →Or open the comparison tool to put any two models side by side, or browse all 578. Or see every Warwick Acoustics headphone in the database, and how much of what this site says about them came from Warwick Acoustics’s own documents.