Can speakers sound worse during break-in period?


I purchased a NOS pr of speakers ( I’m not disclosing their name. Not interested in hearing from their haters) and was really liking them before I started to seriously break them in. It seems like after 24 hours they seem to have changed and sound worse, or not as good as they did. Are they just going through changes with some drivers opening up faster than the others? I know there are many components involved in this process and some might be a head of the others. I’m assuming that’s the case and when everything comes together they will sing.
hiendmmoe
it took hundreds of hours for my von Schweikerts to settle in....when I first listened I was alarmed but stayed the course. 
So perhaps Woofer compliance is the area of most effect ?
That being said, small difference around 30-40 Hz ? 
Audible... doubt it. How does one design, manufacture, sell, something with the promise of perfection upon burn/break in, and at what time table.
And is there planned obsolescence built in as well ?
Perhaps then the answer is to buy certified second hand. Benefit being if you can.., hear something at it's best or worst. Voila' pay half the grossly exaggerated value at new. 
Eat better, buy an exotic car, travel or stay home listening to music sounding the way you like without all the B.S.   
I understand Zu "burn" their drivers in for 400 hours prior to installing them in the cabinet and I believe they still exhibit minor tonal changes after using them in the home.
Whether that is due to the amp or further "burning in" is beyond me.
Do I need to 'burn-in' my Harbeths?No: the only component part of a Harbeth loudspeaker that can change as a result of 'burning-in', is the resin-doped cloth suspension that centres the neck of the cone in the magnetic field - sometimes called the 'spider'. Under the microscope, once the resin-cloth has been worked backwards and forwards, it crazes into millions of small interconnected islands. This process is irreversible and takes only a few hours with bass heavy music played a little louder than normal. After that point, the drive unit can be considered fully stabilised with the resonant frequency settled to its final value. The ferrofluid used in Harbeth tweeters becomes appropriately viscous after a few minutes operation. Neither the coils, resistors, capacitors, cables nor any other part of a Harbeth speaker has any short-term ageing mechanism.

https://www.harbeth.co.uk/speakers/faq.php