Break-in happens in your brain. How on earth would you prove that the materials are changing, and changing enough to be audible. Break-in/burn-in is not a thing, it doesn't matter if you owned and listened to the speakers, your brain was along for the ride and was ALWAYS governing and responsible for the perception. Why do people have such a hard time understanding and accepting reality? It isn't up for debate either, this is well known psychoacoustic science. Embrace science and stop with the fairy-tales.