Mains cable as speaker cable
I have moved into a house and found that the previous owner wired one of the rooms for four speakers using 2.5mm solid copper cable (twin and earth). I am tempted to use this cable as it places the speaker positions up by the ceiling well out of the way of pets, kids etc.
How much difference (I realise this is quite subjective) would it make to the human ear to switch from this to expensive cable? Is there a rule of thumb which can guide me to assess what sort of expense would need to be made on hifi overall before cable had an impact?
If it makes a lot of difference I will simply have to lift up the carpet and install new cable beneath that.
thanks in advance.