Are Open Back Headphones better than Closed back? Reid Stefan compares the sound quality, features, and differences between the two main styles of studio headphones. The Neumann NDH 30 are high impedance open back headphones for mixing and mastering. These headphones are 120 ohms and have a frequency response of 12hz - 34,000hz. Reid monitors through the Prism Titan Audio Interface and compares the M50x closed back low impedance headphones.