The Truthear Zero is 10Ω at 97.5 dB/mW; the Truthear ZERO:BLUE2 is 5.8Ω at 97.1 dB/mW. This page covers what they ask of an amplifier, not how they sound.
In amplifier terms these two are the same headphone. The gap between what they need for 100 dB is under half a decibel, which is smaller than the step between two clicks of most volume controls.
| Specification | Zero | ZERO:BLUE2 |
|---|---|---|
| Impedance | 10 Ω | 5.8 Ω |
| Sensitivity | 97.5 dB/mW | 97.1 dB/mW |
| Sensitivity (voltage) | 117.5 dB/V | 119.5 dB/V |
| Power for 100 dB | 1.8 mW | 1.9 mW |
| Voltage for 100 dB | 0.13 V | 0.11 V |
| Current for 100 dB | 13.3 mA | 18.3 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 1.25 Ω | 0.72 Ω |
| Sources that reach 100 dB out of 280 | 280 | 280 |
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.
41 sources are low enough in output impedance for the Zero under the one-eighth rule but not for the ZERO:BLUE2 (FiiO SnowSky Tiny B, FiiO KA15, FiiO BTR15, 38 more).
280 of the 280 sources here reach 100 dB on both.
The Zero is more demanding than 42% of the 567 non-electrostatic models in this database; the ZERO:BLUE2 than 35%.
| dB SPL | Zero power | Zero voltage | ZERO:BLUE2 power | ZERO:BLUE2 voltage |
|---|---|---|---|---|
| 80 | 0.02 mW | 13 mV | 0.02 mW | 11 mV |
| 85 | 0.06 mW | 24 mV | 0.06 mW | 19 mV |
| 90 | 0.18 mW | 42 mV | 0.19 mW | 34 mV |
| 95 | 0.56 mW | 75 mV | 0.62 mW | 60 mV |
| 100 | 1.8 mW | 0.13 V | 1.9 mW | 0.11 V |
| 105 | 5.6 mW | 0.24 V | 6.2 mW | 0.19 V |
| Source | Price | Headroom, Zero | Headroom, ZERO:BLUE2 | Output impedance | Noise |
|---|---|---|---|---|---|
| JadeAudio JA11 | $20 | 7.2 dB | 4.5 dB | 0.5 Ω | 1.7 µV |
| FiiO KA11 | $29 | 19.4 dB | 16.6 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR11 | $36 | 12.0 dB | 9.2 dB | 0.5 Ω | 8.0 µV |
Of the 280 sources here, 280 reach 100 dB on both. 43 of them also publish an output impedance low enough for both under the one-eighth rule and a noise figure that stays below the audible-hiss threshold with both.
The cheapest of the 43 is the JadeAudio JA11, at $20. It leaves 7.2 dB of headroom on the Zero and 4.5 dB on the ZERO:BLUE2, its output impedance is 0.5 Ω against a one-eighth limit of 1.25 Ω and 0.72 Ω, and its noise figure puts the hiss floor 18 dB and 16 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.
| Model | As printed | Tolerance | Standard |
|---|---|---|---|
| Zero | 20Hz - 39500Hz (IEC61094, Free Field) | not printed | IEC61094 (free field) |
| ZERO:BLUE2 | 20-41kHz (IEC61094, Free Field) | not printed | IEC61094 (free field) |
| 20-20kHz (IEC60318-4, -3dB) | -3 dB | IEC60318-4 |
Truthear prints 20Hz - 39500Hz (IEC61094, Free Field) for the Zero and two ranges, “20-41kHz (IEC61094, Free Field)” and “20-20kHz (IEC60318-4, -3dB)”, for the ZERO:BLUE2.
Zero: The label is printed "Frequency Responce", with the spelling as it stands on the page.
Only one of the two is a specification. The range printed for the ZERO:BLUE2 comes with a tolerance; the one printed for the Zero does not, and a range without a ±dB figure says nothing about how loud that model is at either end of it. The two cannot be compared number against number, however similar they look in the table. Of the 490 models whose maker prints a range, 58 print the tolerance.
Not a measurement; maker by maker.
Both have a page of their own. In full: Truthear Zero and Truthear ZERO:BLUE2. Every figure on this page comes from what Truthear published, or is derived from it — what that maker publishes, counted.