I buy a pair of speakers from a local hifi salon. I get them home, and plug them in, blah. Dissapointed in their performance I call the dealer and try to arrange for a return- but wait!!! It turns out that my new speakers just need to break in! They will sound fine after 250 hrs/ the expiration of my return window!
Thank god I didnt return them because after a couple hundred hours they really opened up! The bass became rock solid, the midrange lost its nasal sound and the tweeters smoothed out.
How does this work you ask? It has to do with electronic components breaking in (they measure the same before and after, but ignore that) and has nothing to do with human nature and our ears simply getting used to something new.
The other great thing is that all speakers break in- they sound markedly different after hours and hours of play- but miraculously, these differences are never for the worse. Only better.
Now we have also learned in this thread that these changes are source dependant! So make sure each source gets a couple hundred hours as the elecronic components and drivers can easily differentiate between sources- even if they output the same voltage! This is not evidence of how crazy this whole premise is!
The moral is that unmeasurable changes take place in parts that have closely matched tolerances. These changes are always for the better- never for the worse and human nature has nothing to do with these differences. Very much like how fluctuations in dirty AC power can make a system sound far worse than it did the day before.
Nothing to do with the fact that you had 10 cups of coffee, flew on an airplane or simply had a bad day.