Short answer
Both are audio interfaces, both at $599.
The SSL 12 reaches 100 dB on 567 of the 567 models here, the Audient iD24 on 561.
| Specification | Audient iD24 | SSL 12 |
|---|---|---|
| Power into 32Ω | 119 mW | 1.2 W |
| Power into 150Ω | 80 mW | 252 mW |
| Power into 300Ω | 58 mW | 126 mW |
| Power into 600Ω | 52 mW | 63 mW |
| Output impedance | 50 Ω | 1 Ω |
| Output noise | not published | not published |
| Price | $599 | $599 |
| Headphones it reaches 100 dB on out of 567 | 561 | 567 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | Audient iD24 | SSL 12 |
|---|---|---|
| 32 Ω | Derived | Upper bound |
| 150 Ω | Derived | Upper bound |
| 300 Ω | Derived | Upper bound |
| 600 Ω | Recomputed | Upper bound |
Neither column is a power rating, and the two are not even weak in the same way. The SSL 12 figures are ceilings worked out from a maximum output voltage, on the assumption that the amplifier holds it into the load. The Audient iD24 figures are worked out from figures its maker did publish — power at other loads, or the voltage printed beside it. The second method understates; the first flatters. That is the wrong way round for reading the table straight across, so a gap in favour of the SSL 12 is the one to doubt.
6 headphones reach 100 dB on the SSL 12 but not on the Audient iD24 — Moondrop COSMO, Moondrop PARA, Symphonium Crimson, 3 more.
546 headphones are left alone by the SSL 12 under the one-eighth rule but coloured by the Audient iD24 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Ocean, 543 more).
561 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 Shure SE846: SSL 12 has +39 dB of headroom there against +29 dB. 10 dB is about 9.5 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Audient iD24 and SSL 12 because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Audient iD24 headroom | SSL 12 headroom | Audient iD24 hiss | SSL 12 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +29 dB damping | +39 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +9 dB damping | +19 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +22 dB damping | +28 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +20 dB damping | +24 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +11 dB damping | +21 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +15 dB | +17 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +9 dB damping | +13 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +5 dB damping | +11 dB | not published | not published |
These two cost the same, $599, so price settles nothing. Out of the 567 models here, the SSL 12 drives 6 models to 100 dB and leaves 546 alone under the one-eighth rule — 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 iD24 and SSL 12.