Speaker Break-In - What Physically Changes During Break-In To Enable Better Sound?

Two key factor's regarding break-in why one should wait 60 to 100 hours.
If you purchased a truly high end 3-way floor stander, where the crossover is on three separate boards, combined with very exotic drivers, then more time is needed for burn-in for the crossovers. The piston's in a new mid-range and woofer are somewhat stiff and should be broken in slowly to avoid off center piston alignment, and play at low volume for at least 60 hours for the piston's to break in to maintain perfect alignment.
If you take a brand new high end speaker right out of the box and crank it at full volume for an extended time, bad mistake. You could permanently throw your piston's out of alignment that could impact the quality of sound especially from the woofer. 

shadorne..Disagree with your assessment on burn-in. In the Spring of 1994 I purchased a used pair of Camber 3.5ti's from a member of the Washington Audio Society. At the time I had a Carver system and one of the two very best CD player's from Denon. Several day's after purchasing, I settled down for a long listening session, and was ticked off since one of the woofer's had severe break up and distortion at low frequencies. The titanium tweeter and woofer were from SEAS. I called the seller and he admitted the first day he had them, he drove them very hard with a low powered tube amp and a high powered solid state amp.
I took the speaker's to a speaker repair service company in Bellevue and was told the piston was damaged and the woofer had to be replaced. The cost of the woofer and repair came to $115.00 and the seller refunded the cost for repair. For those who plan to put speaker's in storage for an extended time, store the speaker's face down. Since the piston is suspended hanging off the back of the cone, the piston will sag if inactive for several years and storing them face down will keep the alignment perfect.

Shadorne-Your not making any sense whatsoever. You need to do more homework.
A piston is a piston, doesn't matter what brand it is if its deemed high end. And unless its burned in at the factory before boxing, which most speaker companies do not have the time for, it will always need to be burned in to loosen up the throw motion of the piston.

zzzzzzzzzzzzzzz.....

shadorne-Hmmm...now let me see..when watching a close-up video on YouTube of a mid-range driver excursion test the cone is constantly moving back and forth on a suspended surround. The constant back and forth motion is caused by a piston moving constantly in and out working just like a car piston which is why the inventor of this type of driver, Edgar Villchur, called it a piston driver in 1952. You really need to do your homework.

shadorne..I neglected to add that the God's were not with Edgar Villchur when he invented his piston driver, he experienced one of the greatest tragedies of all time in audio history and would have been the Bill Gate's of audio and the richest man in high end audio. In 1958 his patent was challenged in Federal Court in New York City and was denied by a federal judge. Since he lost his patent, it prevented him from licensing his patent all over the world to every speaker company and by the early 60's speaker companies everywhere grabbed his design and ran with it. He got so depressed he quit the speaker business in 1958 and made a bundle designing the best hearing aides in the country. His remaining partners that year started up another speaker company called KLH.