On/off, this sets the subwoofer level to reference position, which is typically the standard for most AV equipment standard calibration levels. We recommend using this setting for anyone with home cinema processors or receivers.
Adjustable output volume from -20dB to +20dB in 0.5dB increments. Only available if Ref. Level is set to off.
The input gain will correctly adjust the subwoofer amplifier input gain according to how high the output is from your source. If you know how high the output gain is from your source, here is how to adjust it properly; 1V output set to +6dB, 2V output set to 0dB, 4V output set to -6dB, or 8V output set to -12dB. The -6dB setting works well with most modern AV equipment as their output levels generally are around 4-8V. Analog preamps typically have a lower output voltage.