DT 900 Pro X vs DT 700 Pro X: identical numbers, so the calculator cannot help you
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.
Signal Chain Compatibility Matrix
Select gear and parameters for live gain, impedance and SPL calculations.
Input Equipment Setup
PASS: Optimal Signal Chain
Requires minimum +60dB of clean pre-amp gain. Most budget entry interfaces max out at +50dB to +56dB and introduce hiss at max pot. An inline preamp booster (Cloudlifter CL-1 / FetHead) is strongly recommended.
The interface preamp provides sufficient headroom.
$538
$405
-25%Tonal & acoustic characteristics: Flat, wide-range frequency response for clean music and speech. Smooth, warm acoustic character with air-suspension shock isolation.
Technical advisory: With +69dB max gain, the Gen 4 Solo can drive demanding dynamics like the Shure SM7B natively without requiring an external inline booster.
Physical Interconnect Topology
Shure SM7B
Direct Cable Connection (No Intermediate Box)
1x Shielded Balanced XLR Cable (3-Pin XLR Male to XLR Female)
Focusrite Scarlett Solo (Gen 4)
Host: Apple MacBook Pro (M1/M2/M3/M4)
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.