The volume of the headphones with 48 Ohm impedance and a sensitivity of 114 dB/V is very high under normal use and comparable to the Beyerdynamic 990 Pro. The DT 900 PRO X achieves a nominal sound pressure level (SPL) of 100 dB at 1 mW and 114 dB at 1 V, which makes it very loud and can also be driven well directly from a smartphone.

In comparison, the DT 990 Pro is also an open-back headphone with similar impedance designed for high volumes, but the DT 900 PRO X with STELLAR.45 drivers are specifically optimised for high volumes without sound distortion. This means that the DT 900 PRO X tend to offer better sound quality at high volumes at the same volume.

To summarise: The maximum volume is similar for both models, but the DT 900 PRO X are better designed to deliver high volumes without distortion.