Sennheiser HD 300 PRO - Professional Monitoring Headphones The Sennheiser HD 300 PRO are closed-back circumaural headphones designed for mixing and other pro audio applications. With a frequency response of 6 Hz to 25 kHz, these headphones provide clear reproduction of audio, doing so while offering up to 32 dB of passive noise reduction. Their dynamic drivers offer a linear frequency response throughout the entire spectrum. They are constructed to remain distortion-free, even when pushed to an SPL of up to 123 dB. The HD 300 Pro sports viscoelastic earpads that are intended to be comfortable and facilitate extended, prolonged listening sessions. The isolation of the acoustic drivers within the unit's earcups lends to the experience, bolstering passive noise isolation as well as long-lasting comfort. The included, exchangeable cable measures 4.9 feet and terminates in a 3.5mm connection. A 1/4 inch adaptor is included.