One method of quadraphonic recording on vinyl involved recording from 20Khz to 40Khz, but this information was Frequency Modulated, using a special preamp to decode it. Because it was FM, flat frequency response and low distortion was not required. (Like FM radio).
Nevertheless, the requirement for some kind of sensitivity up to 40KHz caused large improvements in pickup technology, which has benefited us long after quad vinyl died.
Some audiophile recordings have claimed flat response to 22KHz. This is fairly easy to measure simply by looking at the grooves with a microscope.
Nevertheless, the requirement for some kind of sensitivity up to 40KHz caused large improvements in pickup technology, which has benefited us long after quad vinyl died.
Some audiophile recordings have claimed flat response to 22KHz. This is fairly easy to measure simply by looking at the grooves with a microscope.