The 64 Audio Aspire 1 is 11Ω at 104.0 dB/mW; the 64 Audio Fourte is 10Ω at 114.0 dB/mW. This page covers what they ask of an amplifier, not how they sound.
The Aspire 1 needs 10.0 dB more than the Fourte to reach the same loudness — 0.40 mW against 0.04 mW.
| Specification | Aspire 1 | Fourte |
|---|---|---|
| Impedance | 11 Ω | 10 Ω |
| Sensitivity | 104.0 dB/mW | 114.0 dB/mW |
| Sensitivity (voltage) | 123.6 dB/V | 134.0 dB/V |
| Power for 100 dB | 0.40 mW | 0.04 mW |
| Voltage for 100 dB | 66 mV | 20 mV |
| Current for 100 dB | 6.0 mA | 2.0 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 1.38 Ω | 1.25 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.
42 sources stay below the audible-hiss threshold with the Aspire 1 but cross it with the Fourte (Kiwi Ears Allegro Mini, FiiO KA13, Fosi Audio SK02, 39 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 Fourte than 1%.
| dB SPL | Aspire 1 power | Aspire 1 voltage | Fourte power | Fourte voltage |
|---|---|---|---|---|
| 80 | 4.0 µW | 7 mV | 0.4 µW | 2 mV |
| 85 | 0.01 mW | 12 mV | 1.3 µW | 4 mV |
| 90 | 0.04 mW | 21 mV | 4.0 µW | 6 mV |
| 95 | 0.13 mW | 37 mV | 0.01 mW | 11 mV |
| 100 | 0.40 mW | 66 mV | 0.04 mW | 20 mV |
| 105 | 1.3 mW | 0.12 V | 0.13 mW | 35 mV |
| Source | Price | Headroom, Aspire 1 | Headroom, Fourte | Output impedance | Noise |
|---|---|---|---|---|---|
| JadeAudio JA11 | $20 | 14.1 dB | 23.7 dB | 0.5 Ω | 1.7 µV |
| FiiO KA11 | $29 | 26.3 dB | 35.9 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR13 | $59 | 23.2 dB | 32.8 dB | 0.6 Ω | 1.0 µV |
Of the 280 sources here, 280 reach 100 dB on both. 26 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 26 is the JadeAudio JA11, at $20. It leaves 14.1 dB of headroom on the Aspire 1 and 23.7 dB on the Fourte, its output impedance is 0.5 Ω against a one-eighth limit of 1.38 Ω and 1.25 Ω, and its noise figure puts the hiss floor 12 dB and 1 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 |
| Fourte | 5hz – 22kHz | not printed | not printed |
64 Audio prints 20Hz - 18kHz for the Aspire 1 and 5hz – 22kHz for the Fourte.
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 Fourte. Every figure on this page comes from what 64 Audio published, or is derived from it — what that maker publishes, counted.