The 64 Audio Aspire 1 is 11Ω at 104.0 dB/mW; the 64 Audio U12t is 12.6Ω at 108.0 dB/mW. This page covers what they ask of an amplifier, not how they sound.
The Aspire 1 needs 4.0 dB more than the U12t to reach the same loudness — 0.40 mW against 0.16 mW.
| Specification | Aspire 1 | U12t |
|---|---|---|
| Impedance | 11 Ω | 12.6 Ω |
| Sensitivity | 104.0 dB/mW | 108.0 dB/mW |
| Sensitivity (voltage) | 123.6 dB/V | 127.0 dB/V |
| Power for 100 dB | 0.40 mW | 0.16 mW |
| Voltage for 100 dB | 66 mV | 45 mV |
| Current for 100 dB | 6.0 mA | 3.5 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 1.38 Ω | 1.57 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.
3 sources are low enough in output impedance for the U12t under the one-eighth rule but not for the Aspire 1 (FiiO M11S, Singxer SA-1, FiiO M15S).
12 sources stay below the audible-hiss threshold with the Aspire 1 but cross it with the U12t (Lake People G103-S Mk II, Schiit Valhalla 3, Grace Design m900, 9 more).
280 of the 280 sources here reach 100 dB on both.
The Aspire 1 is more demanding than 20% of the 567 non-electrostatic models in this database; the U12t than 8%.
| dB SPL | Aspire 1 power | Aspire 1 voltage | U12t power | U12t voltage |
|---|---|---|---|---|
| 80 | 4.0 µW | 7 mV | 1.6 µW | 4 mV |
| 85 | 0.01 mW | 12 mV | 5.0 µW | 8 mV |
| 90 | 0.04 mW | 21 mV | 0.02 mW | 14 mV |
| 95 | 0.13 mW | 37 mV | 0.05 mW | 25 mV |
| 100 | 0.40 mW | 66 mV | 0.16 mW | 45 mV |
| 105 | 1.3 mW | 0.12 V | 0.50 mW | 79 mV |
| Source | Price | Headroom, Aspire 1 | Headroom, U12t | Output impedance | Noise |
|---|---|---|---|---|---|
| JadeAudio JA11 | $20 | 14.1 dB | 18.7 dB | 0.5 Ω | 1.7 µV |
| FiiO KA11 | $29 | 26.3 dB | 30.9 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR13 | $59 | 23.2 dB | 27.8 dB | 0.6 Ω | 1.0 µV |
Of the 280 sources here, 280 reach 100 dB on both. 51 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 51 is the JadeAudio JA11, at $20. It leaves 14.1 dB of headroom on the Aspire 1 and 18.7 dB on the U12t, its output impedance is 0.5 Ω against a one-eighth limit of 1.38 Ω and 1.57 Ω, and its noise figure puts the hiss floor 12 dB and 8 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.
| Model | As printed | Tolerance | Standard |
|---|---|---|---|
| Aspire 1 | 20Hz - 18kHz | not printed | not printed |
| U12t | 10 Hz – 20 kHz | not printed | not printed |
64 Audio prints 20Hz - 18kHz for the Aspire 1 and 10 Hz – 20 kHz for the U12t.
Neither range has a tolerance printed beside it, so a wider range on one sheet is not deeper bass or more treble.
Not a measurement; maker by maker.
Both have a page of their own. In full: 64 Audio Aspire 1 and 64 Audio U12t. Every figure on this page comes from what 64 Audio published, or is derived from it — what that maker publishes, counted.