Hi, and welcome to Beoworld!!
If your speakers are passive, they will not require any voltage at all and will need an amplifier to drive them. They will just have two wires to connect to a passive link on a stereo. The system, is it a Beocenter 4000? This should have passive inputs that are not voltage dependant. Passive speakers do not require power...
My B&O: 2009 Catalogue and Pricelist