The ACM1-X Audyssey Microphone is individually measured at Audysseys Laboratory in Los Angeles. A serial number is assigned and a unique calibration file is created for each individual microphone. This allows measurements taken with the microphone to be corrected to almost perfectly match those of a "Type 1" reference microphone. In order to take advantage of the benefits of the calibration file, this microphone must be used with Audyssey MultEQ-X software, available in the Microsoft Store on Windows 10 and 11 computers. MultEQ-X requires a paid license for a compatible AVR in order to use the microphone for calibrations. This microphone is equivalent to the ACM1HB microphone that is included with many popular AVR models. NOTE: using this microphone directly with the AVR built-in calibration, or with the mobile MultEQ Editor application will NOT improve the calibration. In order to receive a more precise measurement and resulting calibration, the microphone MUST be used with a paid license for MultEQ-X software downloaded from the Microsoft Store and purchased in-app. The microphone calibration file is downloaded by MultEQ-X, and at this time is only supported for use within the MultEQ-X software. Use of the microphone in other measurement software is NOT currently supported. If you require a replacement microphone to perform the built-in calibration or mobile MultEQ Editor calibration of your Denon or Marantz AVR, please see our other listing for a compatible replacement microphone.