I’ve always wondered whether speaker “break in” or “burn in” actually improves the performance of speakers and/or headphones, or whether it is just another myth perpetuated by elitist yet ignorant audiophiles and commercial entities that take advantage of such individuals.
From the little that I understand, speaker break in should not be necessary for properly designed and constructed speakers. The effects of speaker break in, if they exist at all, are often transient and will disappear within minutes or even seconds after the break in process. Nevertheless, there are supporters of speaker break in, and the speaker break in process should be completely safe.
No single instance of performance deterioration, by a correctly functioning driver, owing to break in, was found.
In other words, if you think speaker break in is a real phenomenon, go ahead and knock yourself out. 
Your speakers should not be any worse off from the break in treatment.
I found these 4 audio files (zipped for your convenience here) that supposedly help break in your speakers when played together, at a moderately loud volume level, for a day or so. Use a media player that supports multiple instances in order to play the files at the same time. Media Player Classic can be set to “Open a new player for each media file played” in Options/Player and “Repeat forever” in Options/Playback.
Download speaker break in audio files:
speaker_breakin.zip (mirror)
Read the following articles on speaker break in and pass your own judgments:
Speaker Break In: Fact or Fiction?
Speakers Burn In
Audax 3-way break-in test
Driver burn in facts
Break-in
The Break-In Process
Speaker break in should not be confused with audio cable break in, which does seem to be an industry perpetuated myth:
Audio Cable “Break In” Science or Psychological?
If you are interested in other audiophile myths, check out this article:
Flushing Out Myths In Consumer Audio
Is it just me or is “voodoo science” extremely wide-spread in the audiophile industry?
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