I have an older sub that came with a home theatre in a box that only has speaker wire hookups and no power hookup. I am considering purchasing a new receiver with a pre out sub connection only. Is there any way to hook the sub up to the receiver or do I need to purchase a new sub. I know I SHOULD purchase a new one, but for right now, do I NEED to buy one. I am thinking of buying the Yahaha HTR-5860.
I would recommend purchasing a new sub. Most of the "subwoofers" that come with HTiB systems are simply the woofers that the main speakers lack.
A great increase in the bass quality would be seen from the purchase of a new woofer.
Also, the bass signal from surround sound formats, be it music or film, are sent out the cable connection to the subwoofer. To utilize the full capabilities of a surround sound receiver, you need to have a subwoofer with this "line level" input. This is the ".1" in the surround format. The subwoofer has its own channel.
However, it was matched to the speakers that came with your old HTiB system, and has a set crossover. More than likely, it will cross over much too high if you try to use it with a good set of mains, and will make the overall sound worse instead of better.
You would be better off scrapping the sub and starting fresh.