The measurement microphone is one of the most critical components of a loudspeaker/room calibration system. Trinnov’s sophisticated algorithms not only rely on very accurate acoustic measurements but also on the ability to localize speakers positions and to detect early reflection provenance. Trinnov’s 3D measurement microphone is the result of our extensive research in 3D sound. We invested a significant amount of time in order to design a tailored measurement system that could gather very precise information regarding spatial position of the sources. This is called triangulation. Each of the 4 omnidirectionnal capsules are placed at the exact same distance from each other, forming a tetrahedric pattern. This allows us to localize each speaker’s placement on both horizontal and vertical planes. – To achieve this challenge, the microphone consists of 4 capsules mounted at the top of thin brass tubes to avoid diffraction. – The capsules form a tetrahedron figure, ideal to identify distance, azimuth and elevation altogether. – To optimize spatial accuracy, all the capsules responses are analyzed and compared recursively to find the best possible matches of 4 and reach a spatial resolution below +/-2° in every direction.