The 64 Audio Ocean is 9.5Ω at 103.7 dB/mW; the 64 Audio U18s is 8Ω at 106.0 dB/mW. This page covers what they ask of an amplifier, not how they sound.
The Ocean needs 2.3 dB more than the U18s to reach the same loudness — 0.43 mW against 0.25 mW.
| Specification | Ocean | U18s |
|---|---|---|
| Impedance | 9.5 Ω | 8 Ω |
| Sensitivity | 103.7 dB/mW | 106.0 dB/mW |
| Sensitivity (voltage) | 123.9 dB/V | 127.0 dB/V |
| Power for 100 dB | 0.43 mW | 0.25 mW |
| Voltage for 100 dB | 64 mV | 45 mV |
| Current for 100 dB | 6.7 mA | 5.6 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 1.19 Ω | 1.00 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.
1 source is low enough in output impedance for the Ocean under the one-eighth rule but not for the U18s (Astell&Kern SR35).
12 sources stay below the audible-hiss threshold with the Ocean but cross it with the U18s (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 Ocean is more demanding than 19% of the 567 non-electrostatic models in this database; the U18s than 9%.
| dB SPL | Ocean power | Ocean voltage | U18s power | U18s voltage |
|---|---|---|---|---|
| 80 | 4.3 µW | 6 mV | 2.5 µW | 4 mV |
| 85 | 0.01 mW | 11 mV | 7.9 µW | 8 mV |
| 90 | 0.04 mW | 20 mV | 0.03 mW | 14 mV |
| 95 | 0.13 mW | 36 mV | 0.08 mW | 25 mV |
| 100 | 0.43 mW | 64 mV | 0.25 mW | 45 mV |
| 105 | 1.3 mW | 0.11 V | 0.79 mW | 80 mV |
| Source | Price | Headroom, Ocean | Headroom, U18s | Output impedance | Noise |
|---|---|---|---|---|---|
| JadeAudio JA11 | $20 | 13.2 dB | 14.8 dB | 0.5 Ω | 1.7 µV |
| FiiO KA11 | $29 | 25.3 dB | 26.9 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR13 | $59 | 22.2 dB | 23.8 dB | 0.6 Ω | 1.0 µV |
Of the 280 sources here, 280 reach 100 dB on both. 48 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 48 is the JadeAudio JA11, at $20. It leaves 13.2 dB of headroom on the Ocean and 14.8 dB on the U18s, its output impedance is 0.5 Ω against a one-eighth limit of 1.19 Ω and 1.00 Ω, and its noise figure puts the hiss floor 11 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 |
|---|---|---|---|
| Ocean | 5 Hz – 22 kHz | not printed | not printed |
| U18s | 10hz – 20kHz | not printed | not printed |
64 Audio prints 5 Hz – 22 kHz for the Ocean and 10hz – 20kHz for the U18s.
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 Ocean and 64 Audio U18s. Every figure on this page comes from what 64 Audio published, or is derived from it — what that maker publishes, counted.