The KZ AS16 Pro is 18Ω at 114.0 dB (no reference unit printed); the KZ ZSX is 24Ω at 111.0 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 ZSX needs 3.0 dB more than the AS16 Pro to reach the same loudness — 0.08 mW against 0.04 mW.
| Specification | AS16 Pro | ZSX |
|---|---|---|
| Impedance | 18 Ω | 24 Ω |
| Sensitivity | 114.0 dB | 111.0 dB |
| Sensitivity (voltage) | 131.4 dB/V | 127.2 dB/V |
| Power for 100 dB | 0.04 mW | 0.08 mW |
| Voltage for 100 dB | 27 mV | 44 mV |
| Current for 100 dB | 1.5 mA | 1.8 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 2.25 Ω | 3.00 Ω |
| Sources that reach 100 dB out of 280 | 280 | 280 |
One caution before reading the rows. KZ AS16 Pro and KZ ZSX 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.
Every source in the database that drives one of them drives the other. On power, the choice between these two changes nothing about what amplifier you need.
13 sources stay below the audible-hiss threshold with the ZSX but cross it with the AS16 Pro (Kiwi Ears Allegro Mini, FiiO K11, FiiO BTR7, 10 more).
280 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: KZ AS16 Pro and KZ ZSX. Each figure on this page is labelled on those pages with where it came from, including the ones KZ never published — what that maker publishes, counted.