How can I make a linked duplicate path with other bevel object? I want to make a cable with an outer sheathing and inside four wires. (Like a simplified version of a KNX-cable, see eg. 
(source: domofox.it)  ).

I want to be able to dynamically modify the curvature of the cable afterwards. 

So I started with a curve, then made a bezier circle and used that as bevel object for the curve, and finally added a solidify modifier for sheathing thickness, works marvelously.

I thought I could just make a linked duplicate of the curve and use a second, new bevel object (smaller) for my linked duplicate path and thus make a smaller conductor which would follow the same path. But when I change the bevel object of the duplicate, it also changes on the original?

How do I get this to work, so I can afterwards change 1 curve and all the others follow the change, each with its own bevel object?
Thanks to Mr.Zak's kind comment, I more or less solved it. I even threw in the twisting of the wires :)
The final solution does not use Bevel objects, but screw and curve modifiers.

In short:


for the wires, I made an object "KNX-wires" that consists of 4 circles
for the sheathing, I made another object "KNX-sheathing", that consists of a single circle
I added a curve "KNX-Path", to define the path of the cable

I then added the following modifiers to "KNX-wires" and "KNX-sheathing": screw, curve (with "KNX-Path" as curve object), solidify (to give some thickness), and a subsurf to finish.


Result looks like this. By changing "KNX-Path" in edit mode, the cable's path changes. By sliding the "KNX-Sheathing" and "KNX-Wires" along the Z-axis, they slide along "KNX-Path" following its curve. By changing the "screw" parameter of the screw modifier, I can change the length of the sheathing and wires (making the wires stick out a bit for instance).