Chasing cables into walls: to cover or not?

[ectoplasm]

I'm half way through chiselling away channels for speaker cables.

However, I am unsure as to whether it's best to cover/encase the cables in plastic trunking before filling with plaster. Is it necessary (plaster shrinkage deforming cables etc) or a waste of time?

[HCking]

its always best to cover them, another option if it is possible in your setup is to put plastic conduit in the walls etc and run some draw strings through so if you ever want to upgrade / change your cables it is possible.