Headphones

At HFN we measure headphone sensitivity as we do loudspeaker sensitivity, as sound pressure level (SPL) output for a given voltage input. With loudspeakers we use a broadband test signal and 2.83V input (as this corresponds to 1W into 8ohm) whereas with headphones we use a 1kHz tone and calculate output for an input of 1V. This gives a result that accords with the volume setting you'll need to use to achieve a given output level – low sensitivity meaning a higher volume control setting, and vice-versa. But a more fundamental measure of drive unit efficacy is current (rather than voltage) sensitivity, because electrical current determines the magnetic field strength developed by the voice coil. In terms of voltage sensitivity, the LCD-1 is a star. But because of its low impedance, its current sensitivity is lower – just 94.6dB SPL for 5mA at 1kHz, almost 20dB shy of the 110.5dB SPL of Beyerdynamic's high impedance T1 Gen 2 headphones [HFN Mar '16] that, conversely, have a much lower 101.3dB voltage sensitivity. KH