This page does not review anything HarmonicDyne 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 |
|---|---|---|---|
| Poseidon | 64 Ω | 103.0 dB | Unit not stated from a shop listing |
| Zeus | 64 Ω | 100.0 dB | Unit not stated from a shop listing |
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 |
|---|---|---|---|
| Poseidon | 10Hz to 40kHz | not printed | not printed |
| Zeus | 10Hz to 40kHz | not printed | not printed |
HarmonicDyne prints a frequency range for both 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 HarmonicDyne 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, give or take a capital letter: “Frequency response”.
2 of these figures stand on a shop listing rather than on anything HarmonicDyne published; those model pages name the shop.
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 2 to drive is the HarmonicDyne Zeus: 1.0 mW and 0.25 V for a 100 dB SPL peak. Their impedances run from 64 to 64 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 2, 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 HarmonicDyne Zeus at 64 Ω, so a source wants an output impedance at or below 8.0 Ω to satisfy the one-eighth rule on everything they make. 135 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.