REW 5.31.3 / UMIK-1 – Unexpectedly low SPL readings

Hello John,

I am trying to measure my DIY loudspeakers using REW 5.31.3 and a miniDSP UMIK-1, but I am getting unexpectedly low SPL readings.

Equipment and settings:

• Windows 11, tested on two computers
• REW 5.31.3
• miniDSP UMIK-1, serial number 7203241
• 0-degree calibration file: 7203241.txt
• Calibration header: Sens Factor =-0.589dB, SERNO: 7203241
• Laptop: Java driver, 48 kHz, UMIK-1 input, channel L
• Windows microphone input volume checked at 100%, audio enhancements disabled
• SPL meter: Z-weighting, Slow

Observations:

1. REW recognizes the calibration file and reports that SPL calibration is not required.
2. The microphone input is approximately -75 dBFS in a quiet room.
3. Normal speech approximately 20 cm directly in front of the microphone produces around -45 dBFS.
4. However, the SPL meter shows only approximately 42 dB SPL while speaking.
5. Another screenshot showed 48.0 dB SPL with -65.69 dBFS.
6. Earlier loudspeaker sweeps produced suspiciously low readings of approximately 25–35 dB SPL.
7. Attempting to increase playback volume to reach the Check Levels target resulted in excessively loud sound.

Disabling REW's Control input volume option did not resolve the issue.

Could you please advise whether these readings indicate an incorrect microphone gain or SPL calibration, and what specific diagnostic check would best identify the cause?

I would like to establish a reliable measurement setup before attempting further loudspeaker sweeps.

Thank you for your help.

Sounds like the cal file may not be being read. Please attach screenshots of the REW soundcard and cal files preferences.