The Moondrop COSMO is 15Ω at 81.8 dB/mW; the Moondrop Old Fashioned is 32Ω at 94.1 dB/mW. This page covers what they ask of an amplifier, not how they sound.
The COSMO needs 12.3 dB more than the Old Fashioned to reach the same loudness — 66 mW against 3.9 mW.
| Specification | COSMO | Old Fashioned |
|---|---|---|
| Impedance | 15 Ω | 32 Ω |
| Sensitivity | 81.8 dB/mW | 94.1 dB/mW |
| Sensitivity (voltage) | 100.0 dB/V | 109.0 dB/V |
| Power for 100 dB | 66 mW | 3.9 mW |
| Voltage for 100 dB | 1.00 V | 0.35 V |
| Current for 100 dB | 66.4 mA | 11.0 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 1.88 Ω | 4.00 Ω |
| Sources that reach 100 dB out of 280 | 188 | 280 |
92 of the 280 sources have the power for the Old Fashioned but not for the COSMO — Apple USB-C dongle (US), Apple USB-C dongle (EU), Generic CX31993 dongles, 89 more.
3 sources are low enough in output impedance for the Old Fashioned under the one-eighth rule but not for the COSMO (Astell&Kern HC3, RME Fireface UFX II, RME Fireface UFX III).
188 of the 280 sources here reach 100 dB on both.
The COSMO is more demanding than 99% of the 567 non-electrostatic models in this database; the Old Fashioned than 79%.
| dB SPL | COSMO power | COSMO voltage | Old Fashioned power | Old Fashioned voltage |
|---|---|---|---|---|
| 80 | 0.66 mW | 100 mV | 0.04 mW | 35 mV |
| 85 | 2.1 mW | 0.18 V | 0.12 mW | 63 mV |
| 90 | 6.6 mW | 0.31 V | 0.39 mW | 0.11 V |
| 95 | 21 mW | 0.56 V | 1.2 mW | 0.20 V |
| 100 | 66 mW | 1.00 V | 3.9 mW | 0.35 V |
| 105 | 209 mW | 1.77 V | 12 mW | 0.63 V |
| Source | Price | Headroom, COSMO | Headroom, Old Fashioned | Output impedance | Noise |
|---|---|---|---|---|---|
| FiiO KA11 | $29 | 5.4 dB | 17.1 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR13 | $59 | 2.3 dB | 14.1 dB | 0.6 Ω | 1.0 µV |
| FiiO KA3 | $79 | 2.3 dB | 15.2 dB | 0.5 Ω | 1.7 µV |
Of the 280 sources here, 188 reach 100 dB on both. 66 of them also publish an output impedance low enough for both under the one-eighth rule and a noise figure that stays below the audible-hiss threshold with both.
The cheapest of the 66 is the FiiO KA11, at $29. It leaves 5.4 dB of headroom on the COSMO and 17.1 dB on the Old Fashioned, its output impedance is 0.7 Ω against a one-eighth limit of 1.88 Ω and 4.00 Ω, and its noise figure puts the hiss floor 35 dB and 26 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.
| Model | As printed | Tolerance | Standard |
|---|---|---|---|
| COSMO | 13Hz- 58kHz (IEC61094, Free Field) | not printed | IEC61094 (free field) |
| 20Hz- 20kHz (IEC60318-4, -3dB) | -3 dB | IEC60318-4 | |
| Old Fashioned | 20Hz - 32kHz (IEC61094, Free Field) | not printed | IEC61094 (free field) |
| 20Hz - 20kHz (IEC60318-4, -3dB) | -3 dB | IEC60318-4 |
Moondrop prints two ranges, “13Hz- 58kHz (IEC61094, Free Field)” and “20Hz- 20kHz (IEC60318-4, -3dB)”, for the COSMO and two ranges, “20Hz - 32kHz (IEC61094, Free Field)” and “20Hz - 20kHz (IEC60318-4, -3dB)”, for the Old Fashioned.
Both sheets print a tolerance, which is rare enough to be worth pointing at: only 58 of the 490 models with a printed range do. These two ranges can be set against each other, because each of them says how far down the response is allowed to be at the ends.
Not a measurement; maker by maker.
Both have a page of their own. In full: Moondrop COSMO and Moondrop Old Fashioned. Every figure on this page comes from what Moondrop published, or is derived from it — what that maker publishes, counted.