I have a similar situation, I have an old dolby pro logic receiver with no subwoofer preout, but it does have speakers a & b. I can use the speakers A to run my bookshelf speakers, but could I use the speakers b output and something like that JL product linked above, to convert the speaker wire to rca, then use a y adapter to create a single rca input for my SVS PB10-NSD? I'm currently using the high level inputs on my Dayton 12" sub, but I would prefer to use the SVS which only has a single rca input jack.