The Beyerdynamic DT 240 Pro is 34Ω at 99.0 dB/mW; the Beyerdynamic DT 770 Pro X Limited is 48Ω at 98.0 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 770 Pro X Limited needs 1.0 dB more than the DT 240 Pro to reach the same loudness — 1.6 mW against 1.3 mW.
| Specification | DT 240 Pro | DT 770 Pro X Limited |
|---|---|---|
| Impedance | 34 Ω | 48 Ω |
| Sensitivity | 99.0 dB/mW | 98.0 dB/mW |
| Sensitivity (voltage) | 113.7 dB/V | 111.2 dB/V |
| Power for 100 dB | 1.3 mW | 1.6 mW |
| Voltage for 100 dB | 0.21 V | 0.28 V |
| Current for 100 dB | 6.1 mA | 5.7 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 4.25 Ω | 6.00 Ω |
| Sources that reach 100 dB out of 280 | 280 | 280 |
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.
1 source is low enough in output impedance for the DT 770 Pro X Limited under the one-eighth rule but not for the DT 240 Pro (Shanling H5).
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 DT 240 Pro and Beyerdynamic DT 770 Pro X Limited. Every figure on this page comes from what Beyerdynamic published, or is derived from it — what that maker publishes, counted.