I have a JBL E100 series speaker where the mid and tweeters are blown, but the 2 big speakers are still good. I want to use it as a sub woofer, but have no idea how? I have a Onkyo TX-NR646 AV receiver I trying to hook to with only 2 subwoofer pre outs. The manual states the need for a pre amp for passive speakers, so I assume this output needs a preamp for what I'm trying to do? Can anyone shed some light on this?