At high resistance: more powerful source is needed; there is less distortion. In studio or Hi-Fi models in need of pure signal, users increase the resistance and must use an additional preamplifier. The average value for all DJ headphones is 30 ˗ 90 Ohms, an additional amplifier is not needed, they all have the ability to sound loud not only from the mixer, but also from a laptop or smartphone. Below 30 Ohms, there may be distortions at large loudness; above 90 Ohms you cannot hear the headphones loudly on the small electronics.