Can speakers sound worse during break-in period?

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.

To all the naysayers I must say I’m sorry your mind is made up and if it can’t be measured on paper it doesn’t exist. I let my ears tell me what the truth is not a set of numbers that try to explain why it’s impossible to hear something if it can’t be measured. I started this post asking a basic question and have now answered that question: yes speakers do go through changes during a break-in process and do sound worse before they get better and better. I’ve now put close to 125 hrs on them and it’s a night and day difference from the first 25 hrs. They have come alive in a way that gives no regret or cause to wish I never bought them. They are the best speakers I’ve ever owned!!!!

They are the best speakers I’ve ever owned!!!!

What are they?