Focusrite Vocaster Two with Superlux HD-681: the cheap headphones are the loud ones
This is a shop bundle, and it computes better than the obvious studio pairing. 32 ohms and 98 dB/mW give 117.2 dB on an interface that manages only 106.3 dB with a 250 ohm DT 990 — 10.9 dB in favour of the cheaper half. The number rests entirely on the voltage side of Focusrite's sheet.
Louder than the studio option by 10.9 dB — and the number rests on voltage alone.
Level. This pairing is a Thomann bundle: Vocaster Two plus Superlux HD-681. Superlux publishes 98 dB/mW at 32 Ω, which converts to 113.0 dB/V. Focusrite publishes 1.64 V. Peak level: 117.2 dB, 7.2 dB above the target. Put the interface's obvious studio partners on the same socket and it goes the other way:
| Headphones | Impedance | Peak SPL | Against 110 dB |
|---|---|---|---|
| Superlux HD-681 | 32 Ω | 117.2 dB | +7.2 dB |
| beyerdynamic DT 770 Pro 80 Ω | 80 Ω | 111.3 dB | +1.3 dB |
| beyerdynamic DT 990 Pro 250 Ω | 250 Ω | 106.3 dB | −3.7 dB |
The cheapest headphones in the table are 10.9 dB louder than the dearest. Cheap is not quiet, and low impedance is loud.
What the datasheet will not settle. Superlux prints one sensitivity and one impedance for the HD681, HD681B and HD681F — three models the same page describes as having three distinctive sound profiles. That cannot hold at every frequency. It does not change the verdict here: even a ±3 dB spread between variants leaves 114.2–120.2 dB, comfortably over.
The pearl: 1.64 V is a voltage, and this load asks for current. Holding 1.64 V across 32 Ω means 51 mA and 84 mW. The only power figure Focusrite publishes for this output is 8.5 mW at 270 Ω — ten times less, at a load 8.4 times higher. So 117.2 dB is an upper bound built entirely on the voltage side of the sheet, and the current side is unpublished. On the 250 Ω row those 8.5 mW barely matter, because 250 Ω is nearly the load they were measured at. On the 32 Ω row they are the whole question.