Seems like the preamp out should work. Some of the rythmik subs have speaker level connections. Which one do you have?
If you have speaker level connections Tee-Jay on YouTube can show you how to do it. He's awesome!
https://youtu.be/Ew7G6H9YoVA
If you have speaker level connections Tee-Jay on YouTube can show you how to do it. He's awesome!
https://youtu.be/Ew7G6H9YoVA