The Beyerdynamic DT 1770 PRO is 250Ω at 102.0 dB/mW; the Beyerdynamic DT 990 Pro (250Ω) is 250Ω at 96.0 dB (no reference unit printed). This page covers what they ask of an amplifier, not how they sound.
The DT 990 Pro (250Ω) needs 6.0 dB more than the DT 1770 PRO to reach the same loudness — 2.5 mW against 0.63 mW.
| Specification | DT 1770 PRO | DT 990 Pro (250Ω) |
|---|---|---|
| Impedance | 250 Ω | 250 Ω |
| Sensitivity | 102.0 dB/mW | 96.0 dB |
| Sensitivity (voltage) | 108.0 dB/V | 102.0 dB/V |
| Power for 100 dB | 0.63 mW | 2.5 mW |
| Voltage for 100 dB | 0.40 V | 0.79 V |
| Current for 100 dB | 1.6 mA | 3.2 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 31.25 Ω | 31.25 Ω |
| Sources that reach 100 dB out of 280 | 280 | 277 |
One caution before reading the rows. Beyerdynamic DT 990 Pro (250Ω) 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.
3 of the 280 sources have the power for the DT 1770 PRO but not for the DT 990 Pro (250Ω) — Apple USB-C dongle (EU), Steinberg UR22C, Sony NW-A306.
277 of the 280 sources here reach 100 dB on both.
The DT 990 Pro (250Ω) is more demanding than 95% of the 567 non-electrostatic models in this database; the DT 1770 PRO than 82%.
| dB SPL | DT 1770 PRO power | DT 1770 PRO voltage | DT 990 Pro (250Ω) power | DT 990 Pro (250Ω) voltage |
|---|---|---|---|---|
| 80 | 6.3 µW | 40 mV | 0.03 mW | 79 mV |
| 85 | 0.02 mW | 71 mV | 0.08 mW | 0.14 V |
| 90 | 0.06 mW | 0.13 V | 0.25 mW | 0.25 V |
| 95 | 0.20 mW | 0.22 V | 0.79 mW | 0.45 V |
| 100 | 0.63 mW | 0.40 V | 2.5 mW | 0.79 V |
| 105 | 2.0 mW | 0.71 V | 7.9 mW | 1.41 V |
| Source | Price | Headroom, DT 1770 PRO | Headroom, DT 990 Pro (250Ω) | Output impedance | Noise |
|---|---|---|---|---|---|
| JadeAudio JA11 | $20 | 7.8 dB | 1.8 dB | 0.5 Ω | 1.7 µV |
| FiiO KA11 | $29 | 16.2 dB | 10.2 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR11 | $36 | 7.6 dB | 1.6 dB | 0.5 Ω | 8.0 µV |
Of the 280 sources here, 277 reach 100 dB on both. 72 of them also publish an output impedance low enough for both under the one-eighth rule and a noise figure that stays below the audible-hiss threshold with both.
The cheapest of the 72 is the JadeAudio JA11, at $20. It leaves 7.8 dB of headroom on the DT 1770 PRO and 1.8 dB on the DT 990 Pro (250Ω), its output impedance is 0.5 Ω against a one-eighth limit of 31.25 Ω for both, and its noise figure puts the hiss floor 27 dB and 33 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.
| Model | As printed | Tolerance | Standard |
|---|---|---|---|
| DT 1770 PRO | 5-40,000Hz | not printed | not printed |
| DT 990 Pro (250Ω) | 5 - 35.000 Hz | not printed | not printed |
Beyerdynamic prints 5-40,000Hz for the DT 1770 PRO and 5 - 35.000 Hz for the DT 990 Pro (250Ω).
Neither range has a tolerance printed beside it, so a wider range on one sheet is not deeper bass or more treble.
Not a measurement; maker by maker.
Both have a page of their own. In full: Beyerdynamic DT 1770 PRO and Beyerdynamic DT 990 Pro (250Ω). 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.