Can speakers sound worse during break-in period?

Huge yes, I heard a huge difference from the first 10 hours until 200 hours, and 300 hours.

 They are much more punchy now, deep, midrange is flawless,  
    Amps, speakers, preamps, CD players, all get better after a couple hundred hours.
capacitors warmed up, I always turn my stereo on the night before, and let everything warm up before critical listening

Here’s a progress report on my speakers break-in process. I’m happy to report after 100hrs ( XLO burn in disc track 9 ) things have improved. They’re starting to open up, driver integration is better and sounding much fuller. They still need more hrs on them but things are starting sound very good.
hiendmmoe

Hello,
Kenjit, Can you explain why a mechanical object breaking in cannot be measured. A woofer gets better excursion over time. It levels out at a point, but definitely changes. Since the driver is just a motor moving air to make sound the more efficient the motor becomes the more nuanced sound it can create. This is most notable at low volumes after the break in period. The same thing happens to a car engine. It actually gets better gas mileage after 5000 miles than it did at mile 100. If I am wrong please explain your comment so I can be educated. 

Break-in is  not only hoax , is some type vendor trick.If any customer
paid for example speakers he did not satisfy and planning to return The vendor say---wait, wait , after 100 hours break in sound will be much more better, and after  time, the guy  used to live and say, Speakers is not bad, sound much better, 

@hshifi.    better excursion over time and similar statement is the legend.   hoax