The ZMF Caldera Closed is 60Ω at 94.0 dB/mW; the ZMF Verite Closed is 300Ω at 99.0 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 Caldera Closed needs 5.0 dB more than the Verite Closed to reach the same loudness — 4.0 mW against 1.3 mW.
| Specification | Caldera Closed | Verite Closed |
|---|---|---|
| Impedance | 60 Ω | 300 Ω |
| Sensitivity | 94.0 dB/mW | 99.0 dB/mW |
| Sensitivity (voltage) | 106.2 dB/V | 104.2 dB/V |
| Power for 100 dB | 4.0 mW | 1.3 mW |
| Voltage for 100 dB | 0.49 V | 0.61 V |
| Current for 100 dB | 8.1 mA | 2.0 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 7.50 Ω | 37.50 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.
19 sources are low enough in output impedance for the Verite Closed under the one-eighth rule but not for the Caldera Closed (Zoom AMS-22, Arturia MiniFuse 2, Arturia MiniFuse 1, 16 more).
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.
Each model has a page of its own with the full source list, the hiss estimate and the provenance of every figure above: ZMF Caldera Closed and ZMF Verite Closed. Every figure on this page comes from what ZMF published, or is derived from it — what that maker publishes, counted.