Check Levels generates a subwoofer or speaker calibration signal at the Sweep Level (the level at which REW generates its measurement sweep, -12 dBFS by default). The replay volume controls, AV processor volume and (if necessary) the Sweep Level need to be adjusted to achieve the in-room SPL at which you wish to measure, typically 75 dB. This level should be checked using your SPL meter, if the SPL is lower or higher than desired adjust the AV processor volume (preferred) or the Sweep Level (if connected directly to an equaliser, subwoofer or amplifier). The initial setting for the AV processor volume should be the same as you normally use for listening.

Wave Volume should be set to 1.0 (full volume), Output Volume should be around 0.5 if it affects the signal level - line outputs usually are not affected by this control, headphone or speaker outputs usually are. REW will set these controls to their last values on startup if the Control output mixer/volume check box has been selected and REW has been able to access the controls, otherwise you can set them manually as required, via the controls above or those in your soundcard's mixer or OS audio level controls. If the output volume control does not affect the output being used it is best to mute it, that prevents any sound from your computer's speakers affecting your measurements.

The input level, if not using a USB microphone, should be around -18 dBFS when the cal signal is playing, if it is lower or higher adjust the Input Volume either using the REW control (if enabled) or your soundcard's mixer or OS audio level controls. The target range is -24 dB to -12 dBFS. Levels higher than -12 dB may result in input clipping during measurement, levels lower than -24 dB give noisier results. If you are using a USB microphone leave the volume control at the unity gain setting, which is selected by default when the mic is first plugged in. The input level with a USB mic will usually be much lower, around -30 to -50 dBFS.

Press Next to start the calibration signal or Cancel to quit.