(The module is installed in the back wall of the subwoofer and connected to the amplifier of your Hi-Fi system with an RCA-Y cable, which is used there between the preamp and the power amplifier instead of the usual wire bridges. In this way, the level of the subwoofer is regulated by the volume control on the amplifier in the same way as the level of the main speakers. The level of the active module and thus the ratio between the subwoofer and the main speakers is preset directly on the amplifier module. In addition, the cut-off frequency and the phase (for adaptation to the installation location) can be set here.)