When connecting two sources to the sub, one source should use RCA and the other should use XLR. If none of your sources have XLR outputs, you can simply use an adapter. it's important to remember that one of the sources also needs a 12 volt trigger output. Mostly all A/V receivers today support 12v trigger, so that shouldn't be an issue. If one of your sources doesn't have a dedicated subwoofer output, you need to run both the left and right signal to the subwoofer to make sure you're feeding it the entire signal.
Once you have everything connected, you have to open the app and select dual source. When the app is opened, select the subwoofer you want to change the settings for. If you only have one subwoofer, only one will show up in the app. Next, press "settings" at the bottom, then "Input / AUTO turn-on". On this page, you will scroll down until you find the "Dual Source" options. Which one to choose, will depend on how you've connected everything. In this example, I use 1 RCA and 12v trigger from my A/V receiver to the sub for one source. The other source uses 2 XLR cables. That means I choose "Mode 4" under the dual source options.
Adjusting settings for each input
With dual source enabled, you can have different settings on the RCA input compared to the XLR input. In many cases you want to have ref. level and LPF bypass enabled for your A/V receiver, but not for your stereo system. To change the settings for the different output, click the "Level" button in the bottom left.
On the next screen, you can switch between RCA and XLR in the top left. This will switch between the memory banks that are enabled for the two different inputs. When you have RCA selected, those settings will only affect the RCA inputs and vice versa when XLR is selected.
With both systems now connected to the subwoofer, all that remains is to properly enjoy the content you want, seamlessly switching between your two sources!