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X curve
Stands for ‘extended’, as opposed to the ‘N’ (normal) curve, which is the same as the Academy Curve.
The ‘X’ curve is also known as the ‘wide-range curve’, and is codified in ISO Bulletin 2969. Specifications call for pink noise — at listening position in a re-recording situation or two-thirds of the way back in a theatre — to be flat to 2 kHz, rolling off 3 dB per octave after that. This curve is found in all motion picture theatres and re-recording stages worldwide.
References
The National Film and Sound Archive of Australia acknowledges Australia’s Aboriginal and Torres Strait Islander peoples as the Traditional Custodians of the land on which we work and live and gives respect to their Elders both past and present.