The AKG K612 Pro is 120Ω at 91.8 dB/mW; the Meze 109 Pro is 40Ω at 112.0 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 AKG K612 Pro needs 20.2 dB more than the Meze 109 Pro to reach the same loudness — 6.6 mW against 0.06 mW.
| Specification | AKG K612 Pro | Meze 109 Pro |
|---|---|---|
| Impedance | 120 Ω | 40 Ω |
| Sensitivity | 91.8 dB/mW | 112.0 dB/mW |
| Sensitivity (voltage) | 101.0 dB/V | 126.0 dB/V |
| Power for 100 dB | 6.6 mW | 0.06 mW |
| Voltage for 100 dB | 0.89 V | 50 mV |
| Current for 100 dB | 7.4 mA | 1.3 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 15.00 Ω | 5.00 Ω |
| Sources that reach 100 dB out of 280 | 277 | 280 |
3 of the 280 sources have the power for the Meze 109 Pro but not for the AKG K612 Pro — Apple USB-C dongle (EU), Steinberg UR22C, Sony NW-A306.
17 sources are low enough in output impedance for the AKG K612 Pro under the one-eighth rule but not for the Meze 109 Pro (Zoom AMS-22, Arturia MiniFuse 2, Arturia MiniFuse 1, 14 more).
13 sources stay below the audible-hiss threshold with the AKG K612 Pro but cross it with the Meze 109 Pro (FiiO BTR11, FiiO K11 R2R, Lake People G103-S Mk II, 10 more).
277 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.
Each model has a page of its own with the full source list, the hiss estimate and the provenance of every figure above: AKG K612 Pro and Meze 109 Pro. Every figure on this page comes from what AKG and Meze published, or is derived from it — what AKG publishes and what Meze publishes, both counted.