Why do I need a special cable?You don’t!the Beosystem 3 has more powerlink sockets and if I use for every Beolab an extra socket (one for left, the other one for right…..) this would not work?Correct, you’re right this would work.
We have this discussed here too ...
/forum/general-discussion-and-questions/2-x-beolab-74-as-stereo-speakers#post-2123003
My B&O Icons: