Does the Goldmund have something that is called HT Bypass or Home Theater bypass? It's specifically used in situations where you wish to have a multichannel setup with a receiver or HT Preamp and a separate integrated or preamp for 2-channel.
In other setups to do this you bypass the bass management of the units and do the bass management in the subwoofer itself. In such instances, the subwoofer has its own binding posts or input and outputs for balanced and unbalanced connections and you pass the signal into the sub and then out from the sub to the amp that's driving the 2-channels L and Rs. Thus, it's the subwoofer's highpass and low pass filters that handle things.
There should be instructions with your sub on how to do this.
In other setups to do this you bypass the bass management of the units and do the bass management in the subwoofer itself. In such instances, the subwoofer has its own binding posts or input and outputs for balanced and unbalanced connections and you pass the signal into the sub and then out from the sub to the amp that's driving the 2-channels L and Rs. Thus, it's the subwoofer's highpass and low pass filters that handle things.
There should be instructions with your sub on how to do this.