Can speakers sound worse during break-in period?

I am most fond of posters who argue one thing one day, and then within the same thread argue exactly the opposite. That kind of gymnastics will always be pretty amazing to watch.

Hello, 
Maybe we are coming at this in different directions. I still believe in what I said, but if I am understanding this is that the speakers should always sound good and get better. Just like my car analogy. If it sounds bad then something else is wrong. The only thing I can think is if you break in with a limited amount of frequencies you may run into some issues. If you play 1khz for a hundred hours then the woofer did not move due to the crossovers.  If break in on a speaker is not real then why do most manufacturers recommend this and tell the dealers to do this? Is there a representative from a speaker manufacturer that can weigh in on this? Maybe the OPs crossover is messed or he had some interference from other things. 

I suspect surrounds on midrange cones and woofers become more supple as they are used. Though that could vary widely depending on the surround material. Usually showing gains in lower frequency response and probably dynamics too. I was also told by a very prominent speaker designer that the caps in the crossover will "sweeten up" with several hundred hours of use. I guess he means the caps become more linear over time and thus differences could be audible and measurable. I would agree that if the speaker in question were to sound bad right out of the box, other problems might exist.

@mr_m 
a very prominent speaker designer that the caps in the crossover will "sweeten up" with several hundred hours of use. I guess he means the caps become more linear over time and thus differences could be audible ,  

This is very interesting , may be the caps is coming more dry or more juice 

Yes, capacitor break in means.... "more juice"

Actually, a capacitor consists of two or more conductive plates which are not connected or touching each other, they electrically separated either by air or by some form of a good insulating material such as waxed paper, mica, ceramic, plastic or some form of a liquid gel as used in electrolytic capacitors. This insulating layer between a capacitors plates is known as the Dielectric.
The dielectric material can interact with current flow. As the cap is used and voltage is passed, the plates can heat up, which very much affects how the skin affect of different dielectrics and resistance (Z) ESR/ESL of the cap. The signal, like water, will take the path of least resistance. It can even create a temporary magnetic field. Different Dielectrics do react with a hysteresis effect differently to all of this in caps. That why an electrolytic, mylar, polyprop, polycarb, teflon, paper in oil etc, all have a unique sound signature. As all of this stabilizes, the caps do settle in and YES, you hear them settle down as they break in. Another common word for this is the caps are FORMING.