The Thieaudio Monarch MKIV is 10Ω at 100.0 dB (no reference unit printed); the Thieaudio Oracle MKII is 15Ω at 104.0 dB (no figure from the maker at all). 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 Monarch MKIV needs 4.0 dB more than the Oracle MKII to reach the same loudness — 1.0 mW against 0.40 mW.
| Specification | Monarch MKIV | Oracle MKII |
|---|---|---|
| Impedance | 10 Ω | 15 Ω |
| Sensitivity | 100.0 dB | 104.0 dB |
| Sensitivity (voltage) | 120.0 dB/V | 122.2 dB/V |
| Power for 100 dB | 1.0 mW | 0.40 mW |
| Voltage for 100 dB | 0.10 V | 77 mV |
| Current for 100 dB | 10.0 mA | 5.2 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 1.25 Ω | 1.88 Ω |
| Sources that reach 100 dB out of 280 | 280 | 280 |
One caution before reading the rows. Thieaudio Monarch MKIV printed a decibel figure with no reference unit, so this page reads it as per milliwatt. If it is really per volt, that model needs far more than the table says. Why the two readings differ by so much. For Thieaudio Oracle MKII the maker publishes no sensitivity figure at all. The number in the table was collected when this database was first built and has never been traced to a manufacturer document, so treat every row below it as an estimate rather than a specification.
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.
5 sources are low enough in output impedance for the Oracle MKII under the one-eighth rule but not for the Monarch MKIV (FiiO KA13, Schiit Vali 2+, FiiO M11S, 2 more).
2 sources stay below the audible-hiss threshold with the Monarch MKIV but cross it with the Oracle MKII (FiiO BTR11, Rupert Neve RNHP).
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: Thieaudio Monarch MKIV and Thieaudio Oracle MKII. Each figure on this page is labelled on those pages with where it came from, including the ones Thieaudio never published — what that maker publishes, counted.