The HD 300 PRO is a closed-back, over-ear monitoring headphone built around a dynamic transducer. It is tuned for a linear, neutral response and low distortion, and it is intended for editing, mixing, recording and live monitoring, including use behind a drum kit or in loud rooms.

The closed passive earcup design attenuates ambient noise by up to 32 dB, while the circumaural viscoelastic earpads and a moderate contact pressure are meant to keep it comfortable over long sessions. Sensitivity is 108 dB SPL per volt and the maximum level is 123 dB SPL, so it can be driven loudly without much distortion.

The headphone connects with a detachable, screw-on 1.5 m cable ending in a 3.5 mm jack, and a screw-on 1/4 inch adapter is supplied. The cable uses the Sennheiser 300 series system connector, so replacement cables, ear cushions and a headband pad are available as accessories.