Is the PreSonus Studio 24c loud enough for the Beyerdynamic DT 900 Pro X?
Both are 48 Ω at 100 dB/mW, both need 0.69 V and 10 mW, both reach 117.4 dB on the weakest interface in this catalogue. Open or closed is an acoustic choice, not an electrical one.
Both: 117.4 dB, 7.4 dB of headroom, on 1.62 V. There is no electrical difference to weigh.
beyerdynamic gives both the DT 900 Pro X and the DT 700 Pro X as 48 Ω and 100 dB SPL (1 mW / 500 Hz) on the same STELLAR.45 driver. That converts to 113.2 dB/V, so a 110 dB peak needs V = 10^((110 − 113.2)/20) = 0.69 V, drawing 10 mW and 14.43 mA. PreSonus publishes no voltage for the Studio 24c, only 47 mW per channel into 56 Ω, from which V = √(0.047 × 56) = 1.62 V — the weakest headphone output of any interface in this catalogue. It still clears both by 7.4 dB. The choice between these two headphones is isolation and soundstage; the numbers are the same digit for digit.
The pearl: «32-300 Ω supported» is not a level specification. PreSonus states a headphone working range of 32 to 300 Ω for the Studio 24c. Read as a promise of loudness it is misleading: a 300 Ω HD 650 on the same output reaches 107.2 dB against a 110 dB target — 2.8 dB short, the volume control at maximum. A working range says the amplifier is stable and undamaged into those loads. Whether it reaches level is a different question with a different number behind it, and only one of the two is usually printed.
Why beyerdynamic made these two 48 Ω. The PRO X line is the company's own answer to the impedance-version problem that the DT 770/880/990 created: one 48 Ω model instead of three, and a driver sensitive enough that an interface no longer needs to be chosen for voltage. It works — the 250 Ω DT 990 needs 2.51 V where the DT 900 Pro X needs 0.69 V, a factor of 3.6 in voltage and 11.2 dB in required source level.
What we cannot check. PreSonus does not publish an output impedance for the Studio 24c. Against 48 Ω the 1/8 rule wants 6 Ω or less; with nothing published, the 117.4 dB above is a ceiling computed as if the divider took nothing, and the tonal balance is unknown rather than fine. Note also that the 1.62 V itself is derived from a power figure at 56 Ω — a single point on a curve, and a load close enough to 48 Ω that the derivation is reasonable, which would not be true if the only published point were at 600 Ω.