Originally Posted by chikoo
Let me give a simple example that one might be able to relate. Does the elastic on your Underwear loosen up just a tad bit after the first few times you wear abd wash it? The difference is subtle, but it is there.
It's closer to a new pair of cotton jeans, the type that aren't pre-washed. They're stiff, as are driver suspensions and surrounds. With flexing they get softer. Most of the process takes place early on, but it continues almost indefinitely. Most new woofers come though with Fs 5 to 10% above spec, while decades old drivers can measure 5 to 10% below spec. Some guitar players change drivers on a fairly regular basis because they don't care for the loss of high end response that comes with age, while others who prefer a more mellow tone search out old drivers, the older the better.
As for the phenomenon of a driver needing an additional break in after non-use, true, also seen in jeans. After being loosened by wearing them a few days you wash them and they're stiff again, though not as stiff as when new. Speaker suspensions do the same thing after resting, but the time to get them flexing right again is only a few seconds. When I measure a cab after not being used I always warm it up a bit, knowing from experience that if I don't it will be out of spec.
BTW, drivers with foam or rubber surrounds need far less break in than those with cloth surrounds, because foam and rubber don't soften nearly as much as cloth does.
IMO all drivers should be broken in by the manufacturer at the factory, but very few are, as break in takes time, and time is money.