The Beyerdynamic DJ 300 PRO X is 48Ω at 115.0 dB (no reference unit printed); the Beyerdynamic DT 1770 PRO is 250Ω at 102.0 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 DT 1770 PRO needs 13.0 dB more than the DJ 300 PRO X to reach the same loudness — 0.63 mW against 0.03 mW.
| Specification | DJ 300 PRO X | DT 1770 PRO |
|---|---|---|
| Impedance | 48 Ω | 250 Ω |
| Sensitivity | 115.0 dB | 102.0 dB/mW |
| Sensitivity (voltage) | 128.2 dB/V | 108.0 dB/V |
| Power for 100 dB | 0.03 mW | 0.63 mW |
| Voltage for 100 dB | 39 mV | 0.40 V |
| Current for 100 dB | 0.8 mA | 1.6 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 6.00 Ω | 31.25 Ω |
| Sources that reach 100 dB out of 280 | 280 | 280 |
One caution before reading the rows. Beyerdynamic DJ 300 PRO X printed a decibel figure with no reference unit, so this page reads it as per milliwatt. If it is really per volt, that model 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.
18 sources are low enough in output impedance for the DT 1770 PRO under the one-eighth rule but not for the DJ 300 PRO X (Zoom AMS-22, Arturia MiniFuse 2, Arturia MiniFuse 1, 15 more).
16 sources stay below the audible-hiss threshold with the DT 1770 PRO but cross it with the DJ 300 PRO X (FiiO BTR11, FiiO K11 R2R, Lake People G103-S Mk II, 13 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: Beyerdynamic DJ 300 PRO X and Beyerdynamic DT 1770 PRO. Each figure on this page is labelled on those pages with where it came from, including the ones Beyerdynamic never published — what that maker publishes, counted.