The Symphonium Giant is 7.0Ω at 88.5 dB/mW; the Symphonium Helios is 8.5Ω at 83.3 dB/mW. 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 Helios needs 5.2 dB more than the Giant to reach the same loudness — 47 mW against 14 mW.
| Specification | Giant | Helios |
|---|---|---|
| Impedance | 7.0 Ω | 8.5 Ω |
| Sensitivity | 88.5 dB/mW | 83.3 dB/mW |
| Sensitivity (voltage) | 110.0 dB/V | 104.0 dB/V |
| Power for 100 dB | 14 mW | 47 mW |
| Voltage for 100 dB | 0.31 V | 0.63 V |
| Current for 100 dB | 44.9 mA | 74.2 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 0.88 Ω | 1.06 Ω |
| Sources that reach 100 dB out of 280 | 252 | 179 |
73 of the 280 sources have the power for the Giant but not for the Helios — FiiO SnowSky Tiny A, FiiO SnowSky Tiny B, FiiO BTR11, 70 more.
34 sources are low enough in output impedance for the Helios under the one-eighth rule but not for the Giant (FiiO SnowSky Tiny B, FiiO BTR15, FiiO BTR5 2021, 31 more).
179 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: Symphonium Giant and Symphonium Helios. Every figure on this page comes from what Symphonium published, or is derived from it — what that maker publishes, counted.