@simna wrote:
How far apart should I put the speakers when placing them front to front and with reverse polarity on one of the speakers?
Somewhere I read 4 inches, but why not as close as you can? Totally together if you can?
A few inches apart should be fine. Try it out and see how much of a difference it makes with regard to their distance and the noise emitted. It doesn't matter in regards to the effect of break-in, that's only a function of how hard and/or long they're driven. Take care though not to work them too hard for extended periods of time, as the noise cancelling effect via the reversed polarity won't give you any real indication of their possible strain.