ABX test

ABX test is a type of double blind testing of audio devices (such as an amplifier or audio player) in which the participants are tested as to whether or not they can discern the difference between said devices by listening. The test involves the use of a so-called ABX box. The box assigns the letter A to one device, B to the other device and the randomly assigns X to either of the two devices. The subject then listens and try's to determine if X is the same as A or B.