I found this thread on the Bastanis forum which discusses the mechanics of speaker burn in some detail and also provides 3 mp3 burn in tracks:
http://www.audioasylum.com/forums/bastanis/messages/432.html
This might be useful for owners of high efficiency wide range drivers in particular.
I don't think that should be applied to any speaker but the exact ones described. He's talking about some sort of flexible cone material - I'm surprised that's a viable approach for cones in general, but granting that it is, it's not how most cones are designed to operate. Usually you want them rigid. An approach designed to soften up the cones wouldn't be so good for a traditional cone, if it did anything at all.
If you think speakers need breakin, 85db of rock music for 8 hours a night should get you what you want in fairly short order. It's how the speaker is designed to be used, so it can't do harm. Messing with square waves is probably unwise.
One of my maxims is: if a speaker needs to be broken in to sound right, the manufacturer ought to do it, as part of his speaker test. Why should he sell you unfinished speakers? If he tells you he doesn't do it because it isn't necessary, he's probably right. If he tells you it's important but won't do it for you, something's wrong and you should consider different speakers. (I'm ruling out commercial email-for-drop shops like Axiom that are probably not structured to do business this way.)
