Re. some of the talk here about phase inversion.

Some years ago I heard of a simple trick (I think it was called the Hafler effect, or something) where if a third speaker was placed in the centre between the two outer speakers and this third speaker was wired by taking the + from one side and the - from the other side, it would result in the centre speaker outputting the 'out-of-phase' information, thereby creating a centre channel of sorts. Is this what the MS does?
Has anyone tried this?