Moondrop COSMO: how much amplifier do you need?

The Moondrop COSMO is 15Ω with a sensitivity of 81.8 dB/mW, which is 100.0 dB/V. To reach 100 dB SPL — genuinely loud, louder than most people listen — it needs 66 mW, or 1.00 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. 149 of 280 sources here have enough headroom. The cheapest portable source that does the job is the FiiO KA11 at $29.

Sensitivity here is in dB per milliwatt. Manufacturers often quote dB per volt instead and leave the unit off, which is the single most common reason online calculators give answers that are 10–15 dB wrong. The converter explains the difference.

Moondrop publishes this as 100 dB/Vrms (@1kHz) — a figure per volt, not per milliwatt. At 15Ω the two differ by 18.2 dB, so the 81.8 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 18 dB easier to drive than it is — which is roughly the difference between a dongle being enough and not being enough.

Source: moondroplab.com. How this data was built.

Most people listen between 75 and 85 dB. The 100 dB row is the one worth planning around: it gives you headroom for dynamic peaks without designing your system for a volume that would damage your hearing in under fifteen minutes. The safe listening calculator puts numbers on that.

Every source in the database, judged at 100 dB SPL into 15Ω. “Headroom” is how much power is left over above what the headphone needs — 10 dB means ten times the required power, which is what you want for dynamic peaks.

Hiss. At 100.0 dB/V these are sensitive enough to reveal a source's own noise floor. The noisiest source in the database, the Schiit Vali 2+, would put its hiss at roughly 8 dB SPL in these headphones — faintly audible in a silent room. The hiss calculator lets you check your own amplifier's noise figure.

Output impedance. At 15Ω these want a source output impedance below 1.88Ω to satisfy the one-eighth rule. 39 of the 280 sources here miss it, the worst being the Bottlehead Crack (OTL kit) at 120.0Ω. Above that threshold the source starts shaping the frequency response. Check yours here.

Or open the comparison tool to put any two models side by side, or browse all 578. Or see every Moondrop headphone in the database, and how much of what this site says about them came from Moondrop’s own documents.