Short answer
Both are desktop DAC/amps, $459 against $349.
The HiFiMAN EF500 reaches 100 dB on 567 of the 567 models here, the WiiM Ultra on 562.
| Specification | HiFiMAN EF500 | WiiM Ultra |
|---|---|---|
| Power into 32Ω | 1.3 W | 150 mW |
| Power into 150Ω | 282 mW | 22 mW |
| Power into 300Ω | 141 mW | 6.0 mW |
| Power into 600Ω | 70 mW | 3.0 mW |
| Output impedance | not published | not published |
| Output noise | not published | not published |
| Price | $459 | $349 |
| Headphones it reaches 100 dB on out of 567 | 567 | 562 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | HiFiMAN EF500 | WiiM Ultra |
|---|---|---|
| Socket | XLR4 | no separate rating |
| Power into 32Ω | 4.5 W | — |
| Power into 300Ω | 480 mW derived | — |
| Output impedance | not published | — |
| Output noise | not published | — |
| Headphones it reaches 100 dB on out of 567 | 567 | — |
Only the HiFiMAN EF500 has a separate balanced rating from its maker; through it, it reaches 100 dB on 567 of the 567 models here. The WiiM Ultra may still have a balanced socket — its spec sheet simply gives no figure for one, so there is nothing to put beside it. Derived figures are worked out from the loads the maker did publish.
| Load | HiFiMAN EF500 | WiiM Ultra |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Published |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. HiFiMAN EF500 publishes at 32 Ω; WiiM Ultra at 32 Ω and at 300 Ω. The other rows are worked out from those.
So the two columns are not equally firm row by row: at 300 Ω only the WiiM Ultra figure is the maker’s own. On those rows the derived number is the one to doubt first.
5 headphones reach 100 dB on the HiFiMAN EF500 but not on the WiiM Ultra — Moondrop PARA, Sennheiser HD 600, Symphonium Crimson, 2 more.
562 of the 567 models here reach 100 dB on both.
Headroom is at a 100 dB SPL peak.
The widest gap on the list is the Sennheiser HD 600: HiFiMAN EF500 has +13 dB of headroom there against -0 dB. 14 dB is about 23 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for HiFiMAN EF500 and WiiM Ultra because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | HiFiMAN EF500 headroom | WiiM Ultra headroom | HiFiMAN EF500 hiss | WiiM Ultra hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +40 dB | +30 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +20 dB | +10 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +29 dB | +19 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +24 dB | +12 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +21 dB | +12 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +18 dB | +4 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +13 dB | -0 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +11 dB | +2 dB | not published | not published |
The HiFiMAN EF500 costs $110 more than the WiiM Ultra. Out of the 567 models here, that difference buys 5 more models driven to 100 dB.
Nothing runs the other way: there is no axis here on which the cheaper of the two does better.
Only published figures count here; blank axes are counted separately.
Each in full: HiFiMAN EF500 and WiiM Ultra.