Just been reading about the famous hafler circuit to get 4-channel surround sound from a 2-channel amp. This is the description: Then I ran a single wire from the right-positive post on the power-amp to the positive post on the right rear speaker. Then (2) a single wire from its negative post to the negative post on the left rear speaker. Then (3) I completed the circuit with a single wire from the left rear's postive post back to the left-positive post on the power-amp. In shorthand: R+ to R+, R- to L-, L+ to L+. That's the famous Hafler Circuit, given to the world by the famous designer David Hafler (and picked up and made into millions of dollars by Mr Dolby). The effect is subtle; it "warms up" the acoustic feel of the room. It isn't time-delay reverb, just an out-of-phase 'difference' between left and right, which itself is neither left nor right. What I want to know is if it is safe for the amp as there is a mention of low impedance dips and dangers Any thoughts?