Thanks for that reply John, and if necessary I will contact the user's group.

The loudspeaker setup is a 12 v powered PC Works Four Point Surround. There are six sockets at the back of the big box, (three rows of two) top two are marked Front - Rear followed by "Audio inputs" in parentheses. There is a ribbon lead with two male pins at either end which I have connected to the Audio Input sockets and the outside two sockets in the tower..

There are also two little auxiliary speakers which I do not intend to use. These would presumably plug into the other sockets which are marked Front Left - Rear Left, and Front Right - Rear Right.

I am familiar with the type of set-up you describe, one powered speaker with a slave(?) coming off it, but this lot isn't like that ...

However if I can't get it up and running by tomorrow morning I will be buying a set-up like that which I know will work, as there is definitely a signal coming from the centre socket.