This page does not review anything Oppo makes. It counts one thing: how much of what this database says about their products came out of their own documents, and how much had to be worked out or left blank.
| Model | Impedance | Sensitivity | Source of the figure |
|---|---|---|---|
| PM-1 | 32 Ω | 102.0 dB/mW | Published per mW |
| PM-2 | 32 Ω | 102.0 dB/mW | Published per mW |
| PM-3 | 26 Ω | 102.0 dB/mW | Published per mW |
Impedance is almost always printed. Sensitivity is the one that goes wrong, because a decibel figure means two very different things depending on whether it is per milliwatt or per volt — about five decibels apart at 300 Ω and eighteen at 16 Ω. The conversion is here.
| Model | As printed | Tolerance | Standard |
|---|---|---|---|
| PM-1 | 10 - 50,000 Hz | not printed | not printed |
| PM-2 | 10 - 50,000 Hz | not printed | not printed |
| PM-3 | 10 - 50,000 Hz | not printed | not printed |
Oppo prints a frequency range for all 3 models here whose sheets have been read.
Not one of those ranges comes with a tolerance in decibels. Without a ±dB figure a range says nothing about how loud the headphone is at either end of it, which puts Oppo with the majority: of the 490 models across this database whose maker prints a range, 58 print the tolerance.
Every range stands under the same heading: “Frequency Response In Free-Field”.
No measurement is published here — only what was printed. The whole count, maker by maker, is in the frequency response audit.
The hardest of the 3 to drive is the Oppo PM-1: 0.63 mW and 0.14 V for a 100 dB SPL peak. Their impedances run from 26 to 32 Ω, which matters because the voltage a headphone wants rises with impedance while the power falls.
280 of the 280 sources here reach 100 dB on all 3, and the cheapest of them is the Apple USB-C dongle (EU) at $9. “Reaches” means the maker’s own published power figure is enough at that load; it is not a judgement of how it sounds.
Their lowest impedance is the Oppo PM-3 at 26 Ω, so a source wants an output impedance at or below 3.2 Ω to satisfy the one-eighth rule on everything they make. 134 of the 169 sources that publish an output impedance manage that.
These counts use figures the source makers published themselves. A product that publishes nothing is not counted as a pass anywhere above, which is why the three numbers differ so much. The collection matcher runs the same arithmetic over whatever you actually own.