Short answer
Both are audio interfaces, both at $199.
The Audient iD4 MkII reaches 100 dB on 561 of the 567 models here, the Focusrite Scarlett 2i2 4th gen on 552.
| Specification | Audient iD4 MkII | Focusrite Scarlett 2i2 4th gen |
|---|---|---|
| Power into 32Ω | 112 mW | 31 mW |
| Power into 150Ω | 75 mW | 19 mW |
| Power into 300Ω | 55 mW | 22 mW |
| Power into 600Ω | 50 mW | 11 mW |
| Output impedance | not published | 50 Ω |
| Output noise | not published | not published |
| Price | $199 | $199 |
| Headphones it reaches 100 dB on out of 567 | 561 | 552 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | Audient iD4 MkII | Focusrite Scarlett 2i2 4th gen |
|---|---|---|
| 32 Ω | Derived | Derived |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Published |
| 600 Ω | Recomputed | Derived |
Only one of these two columns starts from a power rating. Focusrite Scarlett 2i2 4th gen publishes one at 300 Ω; Audient iD4 MkII publishes none at any of these four loads, so its column is worked out from power it published at other loads. Both are arithmetic on a maker’s own figures rather than guesses, and the method used for the Audient iD4 MkII understates rather than flatters — but at 300 Ω is the only load here at which its maker can be held to a figure.
9 headphones reach 100 dB on the Audient iD4 MkII but not on the Focusrite Scarlett 2i2 4th gen — HiFiMAN HE-6se V2, HiFiMAN HE6 Remastered, HiFiMAN Susvara, 6 more.
552 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 HiFiMAN Susvara: Audient iD4 MkII has +4 dB of headroom there against -3 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 Focusrite Scarlett 2i2 4th gen because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Audient iD4 MkII headroom | Focusrite Scarlett 2i2 4th gen headroom | Audient iD4 MkII hiss | Focusrite Scarlett 2i2 4th gen hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +29 dB | +23 dB damping | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +9 dB | +3 dB damping | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +22 dB | +14 dB damping | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +20 dB | +15 dB damping | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +11 dB | +5 dB damping | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +15 dB | +9 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +9 dB | +5 dB damping | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +4 dB | -3 dB damping | not published | not published |
These two cost the same, $199, so price settles nothing. Out of the 567 models here, the Audient iD4 MkII drives 9 models to 100 dB — and on the other side there is no such advantage at all.
Only published figures count here; blank axes are counted separately.
Each in full: Audient iD4 MkII and Focusrite Scarlett 2i2 4th gen.