Short answer
Both are audio interfaces, $199 against $194.
The Audient iD4 MkII reaches 100 dB on 561 of the 567 models here, the Steinberg UR24C on 558.
| Specification | Audient iD4 MkII | Steinberg UR24C |
|---|---|---|
| Power into 32Ω | 112 mW | 80 mW |
| Power into 150Ω | 75 mW | 27 mW |
| Power into 300Ω | 55 mW | 13 mW |
| Power into 600Ω | 50 mW | 6.7 mW |
| Output impedance | not published | not published |
| Output noise | not published | not published |
| Price | $199 | $194 |
| Headphones it reaches 100 dB on out of 567 | 561 | 558 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | Audient iD4 MkII | Steinberg UR24C |
|---|---|---|
| 32 Ω | Derived | Derived |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Derived |
| 600 Ω | Recomputed | Derived |
Neither column is a maker’s power rating at these loads. Of the 280 sources here, 209 publish a figure at at least one load; these two do not, so every row above is derived — between or beyond the loads each maker did publish, holding output voltage as the maker’s own figures imply. The method understates rather than flatters, but it is still arithmetic rather than a rating.
3 headphones reach 100 dB on the Audient iD4 MkII but not on the Steinberg UR24C — Moondrop PARA 2, Moondrop VENUS, Symphonium Triton.
558 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 Audio-Technica ATH-R70X: Audient iD4 MkII has +15 dB of headroom there against +7 dB. 8 dB is about 5.9 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Audient iD4 MkII and Steinberg UR24C because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Audient iD4 MkII headroom | Steinberg UR24C headroom | Audient iD4 MkII hiss | Steinberg UR24C hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +29 dB | +28 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +9 dB | +8 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +22 dB | +19 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +20 dB | +14 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +11 dB | +9 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +15 dB | +7 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +9 dB | +3 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +4 dB | +1 dB | not published | not published |
The Audient iD4 MkII costs $5 more than the Steinberg UR24C. Out of the 567 models here, that difference buys 3 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: Audient iD4 MkII and Steinberg UR24C.