Remember when adding inserts to a audiometer you should use the standard insert to headphone calibration corrections. We recommend that you have your audiometer calibrated to the inserts as soon as is possible. Although some clinical 2 channel audiometers allow for separate calibration channels for inserts and head phones the factory uses a default number unless the inserts are ordered with the audiometer. Adding to a 2 channel still requires the inserts be calibrated for accurate results.