The Letshuoer S12 Pro is 16Ω at 102.0 dB/mW; the Moondrop Variations is 15.2Ω at 99.8 dB/mW. This page is only about what they ask of an amplifier — not how they sound, which no specification on either sheet can tell you.
The Moondrop Variations needs 2.2 dB more than the Letshuoer S12 Pro to reach the same loudness — 1.0 mW against 0.63 mW.
| Specification | Letshuoer S12 Pro | Moondrop Variations |
|---|---|---|
| Impedance | 16 Ω | 15.2 Ω |
| Sensitivity | 102.0 dB/mW | 99.8 dB/mW |
| Sensitivity (voltage) | 120.0 dB/V | 118.0 dB/V |
| Power for 100 dB | 0.63 mW | 1.0 mW |
| Voltage for 100 dB | 0.10 V | 0.13 V |
| Current for 100 dB | 6.3 mA | 8.3 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 2.00 Ω | 1.90 Ω |
| Sources that reach 100 dB out of 280 | 280 | 280 |
Every source in the database that drives one of them drives the other. On power, the choice between these two changes nothing about what amplifier you need.
3 sources are low enough in output impedance for the Letshuoer S12 Pro under the one-eighth rule but not for the Moondrop Variations (Astell&Kern HC3, RME Fireface UFX II, RME Fireface UFX III).
280 of the 280 sources here reach 100 dB on both. That count is about power only — the output-impedance and hiss lines above are separate questions, and a source can pass this one and fail those.
The gap between these two in decibels does not change with volume — it is a property of the two headphones. What changes is the size of the numbers, and it changes fast: every 10 dB costs ten times the power. The row that matters is the one nearest the level you listen at, and for most people that is nearer the top of this table than the bottom.
The Moondrop Variations is more demanding than 40% of the 567 non-electrostatic models in this database; the Letshuoer S12 Pro than 33%. Both figures use the same measure as the rest of the site: whichever runs out first against a 2 V, 100 mW dongle, voltage or power.
| dB SPL | Letshuoer S12 Pro power | Letshuoer S12 Pro voltage | Moondrop Variations power | Moondrop Variations voltage |
|---|---|---|---|---|
| 80 | 6.3 µW | 10 mV | 0.01 mW | 13 mV |
| 85 | 0.02 mW | 18 mV | 0.03 mW | 22 mV |
| 90 | 0.06 mW | 32 mV | 0.10 mW | 40 mV |
| 95 | 0.20 mW | 57 mV | 0.33 mW | 71 mV |
| 100 | 0.63 mW | 0.10 V | 1.0 mW | 0.13 V |
| 105 | 2.0 mW | 0.18 V | 3.3 mW | 0.22 V |
105 dB is included because forum power figures are usually quoted there or higher. It is also a level that damages hearing in minutes — how many minutes is its own calculator.
| Source | Price | Headroom, Letshuoer S12 Pro | Headroom, Moondrop Variations | Output impedance | Noise |
|---|---|---|---|---|---|
| JadeAudio JA11 | $20 | 13.8 dB | 11.3 dB | 0.5 Ω | 1.7 µV |
| FiiO KA11 | $29 | 25.9 dB | 23.5 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR11 | $36 | 18.5 dB | 16.1 dB | 0.5 Ω | 8.0 µV |
Of the 280 sources here, 280 reach 100 dB on both. That is the easy axis. 69 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 rest either fail one of those or never printed the number at all, and 208 of them are in the second group.
The cheapest of the 69 is the JadeAudio JA11, at $20. It leaves 13.8 dB of headroom on the Letshuoer S12 Pro and 11.3 dB on the Moondrop Variations, its output impedance is 0.5 Ω against a one-eighth limit of 2.00 Ω and 1.90 Ω, and its noise figure puts the hiss floor 15 dB and 17 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.
Cheapest that satisfies three published numbers is not the same as best, and none of it is about how either headphone sounds. To put either model against a source this page does not mention, or to change the target loudness, use the amplifier matcher.
| Model | As printed | Tolerance | Standard |
|---|---|---|---|
| Letshuoer S12 Pro | nothing printed | — | — |
| Moondrop Variations | 9-40kHz (IEC61094, Free Field) | not printed | IEC61094 (free field) |
| 20-20kHz (IEC60318-4, -3dB) | -3 dB | IEC60318-4 |
Letshuoer prints nothing at all for the S12 Pro. Moondrop prints two ranges, “9-40kHz (IEC61094, Free Field)” and “20-20kHz (IEC60318-4, -3dB)”, for the Variations.
So one side of this comparison has a frequency-response number and the other does not — which changes less than it looks. The range printed for the Moondrop Variations does carry a tolerance, which makes it one of only 58 such models out of the 490 with a printed range — a specification rather than a headline. Against a sheet with no range at all there is still nothing to set it beside.
None of this is a measurement. What each maker publishes, and what it is worth, is set out in the frequency response audit.
Each model has a page of its own with the full source list, the hiss estimate and the provenance of every figure above: Letshuoer S12 Pro and Moondrop Variations. Every figure on this page comes from what Letshuoer and Moondrop published, or is derived from it — what Letshuoer publishes and what Moondrop publishes, both counted.