COMPARING SENSITIVITIES

摘要

We use voltage sensitivity as a measure of how loud headphones or speakers will play at a given volume setting because the amplifiers we use are usually voltage sources which aim to deliver constant signal voltage regardless of load impedance. But as it is voice coil current that determines the force acting on the diaphragm, hence its acceleration and the sound pressure level it generates, it is to current sensitivity that we must look to compare the inherent sensitivity of speakers or headphones with different impedances. In the case of the TH-900, its 1 kHz voltage sensitivity of 114.9dB for 1 Vrms and impedance at that frequency of 24.9ohm equates to a current sensitivity of 114.9dB for 40.2mA or 102.8dB for 10mA. The same calculation for the Beyerdynamic T1 (99.6dB, 626ohm) reveals a current sensitivity of 115.5dB for 10mA, an improvement of 4.3x.