The HiFiMAN HE400i 2020 is 35Ω at 93.0 dB (no reference unit printed); the HiFiMAN Susvara is 60Ω at 83.0 dB (no reference unit printed). This page is only about what they ask of an amplifier — not how they sound, which no specification on either sheet can tell you.
The Susvara needs 10.0 dB more than the HE400i 2020 to reach the same loudness — 50 mW against 5.0 mW.
| Specification | HE400i 2020 | Susvara |
|---|---|---|
| Impedance | 35 Ω | 60 Ω |
| Sensitivity | 93.0 dB | 83.0 dB |
| Sensitivity (voltage) | 107.6 dB/V | 95.2 dB/V |
| Power for 100 dB | 5.0 mW | 50 mW |
| Voltage for 100 dB | 0.42 V | 1.73 V |
| Current for 100 dB | 12.0 mA | 28.9 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 4.38 Ω | 7.50 Ω |
| Sources that reach 100 dB out of 280 | 280 | 231 |
One caution before reading the rows. HiFiMAN HE400i 2020 and HiFiMAN Susvara printed a decibel figure with no reference unit, so this page reads it as per milliwatt. If it is really per volt, each of them needs far more than the table says. Why the two readings differ by so much.
49 of the 280 sources have the power for the HE400i 2020 but not for the Susvara — Apple USB-C dongle (US), Apple USB-C dongle (EU), Generic CX31993 dongles, 46 more.
1 source is low enough in output impedance for the Susvara under the one-eighth rule but not for the HE400i 2020 (Shanling H5).
231 of the 280 sources here reach 100 dB on both. That count is about power only — the output-impedance and hiss lines above are separate questions, and a source can pass this one and fail those.
Each model has a page of its own with the full source list, the hiss estimate and the provenance of every figure above: HiFiMAN HE400i 2020 and HiFiMAN Susvara. Each figure on this page is labelled on those pages with where it came from, including the ones HiFiMAN never published — what that maker publishes, counted.