I am interested in characterizing various component stereo 2.1 systems (no AVR), particularly room effects and subwoofer integration, with REW's SPL Meter. Setup: REW V5.19 Beta 9 on Win 10 64-bit fully updated on Dell laptop. New miniDSP UMIK-1 USB Microphone. Connect laptop audio output to desktop speakers through an ifi nano iOne USB DAC (mostly irrelevant to this topic). Cal. Reference: REED R8090 Sound Level Calibrator (purchased 10/2017, accuracy spec +/- 0.5dB, Selectable 1KHz tones at 94 dB & 114dB) REW settings: Preferences > Soundcard > Driver > Java. Preferences > Mic/Meter > Mic or Z weighted SPL meter File: download miniDSP cal. file for my serial number. Issue 1 Preferences > Soundcard > Input > Direct input I insert the UMIK-1 into the REED R8090 and use the REW SPL Meter Calibrate Button. This works but the cal is lost when I close down and restart REW. My workaround, which is undesirable, is to find the one particular Windows Microphone Level setting (-4.1dB for my system) which effectively retains the calibration upon restart. For any other WIndows Level setting, I need to painfully recalibrate each time I restart REW. Issue 2 Preferences > Soundcard > Input > MICROPHONE (Master Volume). In this case, REW uses the UMIK-1 calibration file to self-calibrate, independent of the WIndows Microphone Level setting. Works nicely, except when I check accuracy, by inserting the microphone into the REED R8090, the REW SPL Meter always displays 99dB instead of 94dB. So REW SPL reads about 5dB too high, assuming my cal source is correct. I have used this cal source with an inexpensive stand-alone SPL meter (American Recorder Model SPL-8810), and have no indication that the cal source is off by 5dB. Is there a setting that needs to be changed within the microphone, within REW, or should I modify the cal file sensitivity value by 5dB? Thanks for your attention.