When you connect the CM-10, CM-20, or C550H calibration microphones to the XLR connector on the DM-RTA there are a couple of steps to take to setup the mic.
Open the DM-RTA software, in the top right corner you will see a button labeled 48V. All of our calibration microphones require phantom 48V power so go ahead and select the 48V button so it is highlighted.
Next, select the SPL meter tab and then select the Ref mic drop down menu.
Select the microphone you are using, at the top of the screen you will note the Mic Gain slider has changed and Microphone is selected. The Mic Gain is now set for that particular microphone.
For instructions on how to install the DM-RTA software (Windows) click here.