This page does not review anything Softears 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 |
|---|---|---|---|
| RSV | 8 Ω | 104.0 dB/mW | Converted from per volt |
| Studio4 | 12 Ω | 103.8 dB/mW | Converted from per volt |
| Twilight | 16 Ω | 105.0 dB/mW | Converted from per volt |
| Volume | 5 Ω | 100.7 dB/mW | Converted from per volt |
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 |
|---|---|---|---|
| RSV | 5-40kHz | not printed | not printed |
| 20-20kHz | not printed | not printed | |
| Studio4 | 5-40kHz (1/4' free field, -3Db) | -3 dB | 1/4″ free field |
| 20-20kHz (IEC60318-4) | not printed | IEC60318-4 | |
| Twilight | 8-40kHz(1/4' free field，-3dB) | -3 dB | 1/4″ free field |
| 20-20kHz（IEC60318-4） | not printed | IEC60318-4 | |
| Volume | 8- 40kHz(1/4 inch free field microphone, -5 dB) | -5 dB | 1/4″ free field |
| 20- 20kHz (IEC60318-4) | not printed | IEC60318-4 |
Softears prints a frequency range for all 4 models here whose sheets have been read.
3 of those 4 ranges carry a tolerance in decibels and the rest do not. A range without a ±dB figure says nothing about how loud the headphone is at the ends of it, so within one maker’s own catalogue some of these rows are specifications and some are headlines.
3 of them also name the measurement standard the range was taken under.
The rows are not even called the same thing twice: 4 different headings across 4 models (“Effective frequency response”, “Effective range”, “Frequency range”, and more).
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 4 to drive is the Softears Twilight: 0.32 mW and 71 mV for a 100 dB SPL peak. Their impedances run from 5 to 16 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 4, 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.
On hiss the count is smaller, because most of the industry does not publish a noise figure at all: of the 83 sources here that do, 73 stay under the threshold of hearing on all 4 of their in-ears. The one to watch is the Softears RSV at 125 dB/V — the more sensitive the in-ear, the more of the amplifier’s own noise you hear.
Their lowest impedance is the Softears Volume at 5 Ω, so a source wants an output impedance at or below 0.62 Ω to satisfy the one-eighth rule on everything they make. 80 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.
Almost everything this site says about Softears came from them. That is not the normal case and it is worth saying out loud.
The rule used here is the same for every maker and is described on the manufacturer index. Every figure behind it can be opened on the product page it came from, with the document it came from linked.