The Beyerdynamic DT 990 Edition (600Ω) is 600Ω at 96.0 dB (no reference unit printed); the Beyerdynamic MMX 330 PRO is 48Ω at 96.0 dB/mW. This page covers what they ask of an amplifier, not how they sound.
In amplifier terms these two are the same headphone. The gap between what they need for 100 dB is under half a decibel, which is smaller than the step between two clicks of most volume controls.
| Specification | DT 990 Edition (600Ω) | MMX 330 PRO |
|---|---|---|
| Impedance | 600 Ω | 48 Ω |
| Sensitivity | 96.0 dB | 96.0 dB/mW |
| Sensitivity (voltage) | 98.2 dB/V | 109.2 dB/V |
| Power for 100 dB | 2.5 mW | 2.5 mW |
| Voltage for 100 dB | 1.23 V | 0.35 V |
| Current for 100 dB | 2.0 mA | 7.2 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 75.00 Ω | 6.00 Ω |
| Sources that reach 100 dB out of 280 | 266 | 280 |
One caution before reading the rows. Beyerdynamic DT 990 Edition (600Ω) 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.
14 of the 280 sources have the power for the MMX 330 PRO but not for the DT 990 Edition (600Ω) — Apple USB-C dongle (US), Apple USB-C dongle (EU), JadeAudio JA11, 11 more.
33 sources are low enough in output impedance for the DT 990 Edition (600Ω) under the one-eighth rule but not for the MMX 330 PRO (Zoom AMS-22, Audient EVO 4, ART HeadAmp 4 Pro, 30 more).
266 of the 280 sources here reach 100 dB on both.
The DT 990 Edition (600Ω) is more demanding than 98% of the 567 non-electrostatic models in this database; the MMX 330 PRO than 79%.
| dB SPL | DT 990 Edition (600Ω) power | DT 990 Edition (600Ω) voltage | MMX 330 PRO power | MMX 330 PRO voltage |
|---|---|---|---|---|
| 80 | 0.03 mW | 0.12 V | 0.03 mW | 35 mV |
| 85 | 0.08 mW | 0.22 V | 0.08 mW | 62 mV |
| 90 | 0.25 mW | 0.39 V | 0.25 mW | 0.11 V |
| 95 | 0.79 mW | 0.69 V | 0.79 mW | 0.20 V |
| 100 | 2.5 mW | 1.23 V | 2.5 mW | 0.35 V |
| 105 | 7.9 mW | 2.18 V | 7.9 mW | 0.62 V |
| Source | Price | Headroom, DT 990 Edition (600Ω) | Headroom, MMX 330 PRO | Output impedance | Noise |
|---|---|---|---|---|---|
| FiiO KA11 | $29 | 6.4 dB | 17.3 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR13 | $59 | 3.0 dB | 14.2 dB | 0.6 Ω | 1.0 µV |
| iBasso DC03 Pro | $69 | 3.2 dB | 14.2 dB | 0.12 Ω | 0.9 µV |
Of the 280 sources here, 266 reach 100 dB on both. 67 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 67 is the FiiO KA11, at $29. It leaves 6.4 dB of headroom on the DT 990 Edition (600Ω) and 17.3 dB on the MMX 330 PRO, its output impedance is 0.7 Ω against a one-eighth limit of 75.00 Ω and 6.00 Ω, and its noise figure puts the hiss floor 37 dB and 26 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 990 Edition (600Ω) | 5 - 35.000 Hz | not printed | not printed |
| MMX 330 PRO | 5 - 40,000 Hz | not printed | not printed |
Beyerdynamic prints 5 - 35.000 Hz for the DT 990 Edition (600Ω) and 5 - 40,000 Hz for the MMX 330 PRO.
DT 990 Edition (600Ω): Beyerdynamic prints one range for the whole DT 990 Edition page, the same figure for every impedance version.
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 990 Edition (600Ω) and Beyerdynamic MMX 330 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.