This page does not review anything 64 Audio 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 |
|---|---|---|---|
| Aspire 1 | 11 Ω | 104.0 dB/mW | Published per mW |
| Fourte | 10 Ω | 114.0 dB/mW | Published per mW |
| Nio | 6 Ω | 105.0 dB/mW | Published per mW |
| Ocean | 9.5 Ω | 103.7 dB/mW | Published per mW |
| Solo | 16 Ω | 100.0 dB/mW | Published per mW |
| U12t | 12.6 Ω | 108.0 dB/mW | Published per mW |
| U18s | 8 Ω | 106.0 dB/mW | Published per mW |
| U4s | 11 Ω | 107.0 dB/mW | Published per mW |
| U6t | 9 Ω | 98.0 dB/mW | Published per mW |
| Volur | 6.3 Ω | 103.0 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 |
|---|---|---|---|
| Aspire 1 | 20Hz - 18kHz | not printed | not printed |
| Fourte | 5hz – 22kHz | not printed | not printed |
| Nio | 10hz – 20kHz | not printed | not printed |
| Ocean | 5 Hz – 22 kHz | not printed | not printed |
| Solo | 20 Hz – 20 kHz | not printed | not printed |
| U12t | 10 Hz – 20 kHz | not printed | not printed |
| U18s | 10hz – 20kHz | not printed | not printed |
| U4s | 10hz – 20kHz | not printed | not printed |
| U6t | 20hz – 20kHz | not printed | not printed |
| Volur | 5hz – 22kHz | not printed | not printed |
64 Audio prints a frequency range for all 10 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 64 Audio 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”.
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 10 to drive is the 64 Audio Solo: 1.0 mW and 0.13 V for a 100 dB SPL peak. Their impedances run from 6 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 10, 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, 36 stay under the threshold of hearing on all 10 of their in-ears. The one to watch is the 64 Audio Fourte at 134 dB/V — the more sensitive the in-ear, the more of the amplifier’s own noise you hear.
Their lowest impedance is the 64 Audio Nio at 6 Ω, so a source wants an output impedance at or below 0.75 Ω to satisfy the one-eighth rule on everything they make. 85 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 64 Audio 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.