Can you point me to a description of what changes occur in the driver that cause break-in? I've never seen an explanation that went beyond "it's a mechanical thing," and I've never seen any measurements that support the claim.
Hey Rex, besides the links someone would post here's some idea about what you ask:
to make it simple, there're two moving parts involved in a speaker: the rear one, which works similarly to a piston and a cylinder; and the front one, usually made by a paper foil pushed back and forward by the rear one.
The movements have to be as accurate (and
analog(ic) to the signal feeding the loudspeaker) as possible, in order for the most exact reproduction of the input to be performed.
Since the inputted signal is typically very rich (harmonically complex) and fast (the moving parts may have to be moving up to 20,000 times per second, as we all know), every single micro-movement performed by the two parts must be perfect; and, on such a scale of accuracy, any alteration of the perfect response of the two parts ends up in an altered sound.
For example, the ideal cone membrane (diaphragm) is a disk with no mass, no aerodynamic friction, no inertia, and completely isotropic (meaning, its characteristics don't change from point to point so the mechanical wave reaching it from the piston is transmitted to the air as accurately as possible).
It's easily seen that there're many things that can change the ideal response: static and dynamic friction in the cylinder/piston system, for example, and even a membrane which is not completely flexible and therefore doesn't transmit the cylinder's movement to the air in a transparent way.
Usually all these aspects do improve after the loudspeaker has being working long enough: micro frictions fade away, the membrane becomes "smoother".
Imagine you have a paper handkerchief made of thin pasteboard: if you start scratching and "working" it between your hands, it become softer, its hard fibers get broken; on the whole, it becomes less rigid, more "coherent", and its response to small movements gets smoother.
Of course a loudspeaker is a much more advanced device than a handkerchief: so the before/after differences are not so meaningful. But you get the idea.
HTH!
Disclaimer: not being a native English speaker, I've tried to be simple and "to the point". I would have benefited by a more complex vocabulary and a greater ability to articulate my thoughts tho. I realize some sentence may sound naive, but thought it's the content that matters X)
