there's not really a lot of information on these. They are part of an "integrated" yhere all pieces are designed to only work with other pieces if that particular system.
If this helps, here's a link yo your owners manual.
http://www.manualslib.com/manual/540055/Sanyo-Dc-Dav821.html
If it's any consolation, it looks like it
MIGHT be a biamp setup which would make them pretty useless without the main unit..