The Beyerdynamic DT 240 Pro is 34Ω at 99.0 dB/mW; the Beyerdynamic MMX 330 PRO is 48Ω at 96.0 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 MMX 330 PRO needs 3.0 dB more than the DT 240 Pro to reach the same loudness — 2.5 mW against 1.3 mW.
| Specification | DT 240 Pro | MMX 330 PRO |
|---|---|---|
| Impedance | 34 Ω | 48 Ω |
| Sensitivity | 99.0 dB/mW | 96.0 dB/mW |
| Sensitivity (voltage) | 113.7 dB/V | 109.2 dB/V |
| Power for 100 dB | 1.3 mW | 2.5 mW |
| Voltage for 100 dB | 0.21 V | 0.35 V |
| Current for 100 dB | 6.1 mA | 7.2 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 MMX 330 PRO 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 MMX 330 PRO. Every figure on this page comes from what Beyerdynamic published, or is derived from it — what that maker publishes, counted.