DT 990 Pro 80 ohm or 250 ohm on a Scarlett 2i2 4th Gen: which is actually louder?
Two versions of one headphone on the best-selling interface, and the answer is not the one the impedance suggests. The 80 ohm version reaches 110.5 dB, the 250 ohm one 108.2 — and both sit under the 8x output-impedance rule. The whole comparison rests on a sensitivity figure beyerdynamic prints once, for both versions, without ever naming the unit.
The 80 ohm version is the louder one here — by 2.3 dB — and both versions fail the output-impedance rule.
Level. The Scarlett 2i2 4th Gen publishes 2.45 V and a 50 Ω output impedance. That resistor and the headphones form a divider, so what reaches the driver is less than 2.45 V:
| Version | Reaches the driver | Peak SPL | Against the 110 dB target | Z ratio |
|---|---|---|---|---|
| DT 990 Pro 80 Ω | 1.51 V | 110.5 dB | +0.5 dB | 1.6 |
| DT 990 Pro 250 Ω | 2.04 V | 108.2 dB | −1.8 dB | 5.0 |
The 250 Ω version needs 2.51 V to reach 110 dB, the 80 Ω one needs 1.42 V — 4.9 dB apart. The higher impedance is the quieter one, which is the opposite of what «the 250 ohm needs an amplifier» implies about the mechanism.
Tonal balance. The rule wants the load to be at least eight times the source. 80 Ω against 50 Ω is 1.6; 250 Ω against 50 Ω is 5.0. Both are under, so neither version escapes the lift at the driver's bass impedance peak — the 250 Ω one is simply three times further along.
The pearl: beyerdynamic prints one sensitivity for two different voice coils, and never names the unit. The datasheet lists «80 Ω / system» and «250 Ω / system» with separate weights and separate cables, then a single «Nominal SPL . . . 96 dB» for both. We read it as dB/mW, following how beyerdynamic spells the unit out on the Amiron: «102 dB (1 mW / 500 Hz)». Read the same 96 dB as dB/V instead and this page inverts: 99.6 dB for the 80 Ω version, 102.2 dB for the 250 Ω one — the 250 becomes the louder of the two by 2.6 dB. One missing unit reverses the ranking of the two products the sheet is comparing.