According to your speaker's webpage those are both inputs on the "left" speaker, so since the line is not an output, that's why your sub doesn't work as it's not getting a signal. Only way I see of using this gear together is to run the sub simultaneously with the "right" speaker via the speaker output, with another length of speaker wire run to the speaker level input on the sub, then use the speaker level output on the sub to your speaker. Most sub-bass is mono so you're not going to miss much. Why did you try to pair these units?