The story is that I have cables for a 7.1 system and currently using Yamaha RX-V640 receiver. During DVD playback the receiver switches off and when you switch it back on it says "CHECK SP WIRES" - meaning there is a problem. I have narrowed it down to only one wire - it goes to one of the two rear centre speakers. Everything used to work perfectly until i had new floors laid. During laying of the new floors my guess is that the tradesmen have hammered at least one nail into this wire! Trouble is that the wire is now under a wooden plant which is held by lots of nails (one or more of which are probably causing a problem). How does one go about locating the offending nail in a speaker wire ? Is there fast and easy way of doing it? Perhaps using some specialised equipment ?