MoFi 888 making me mad!

traudio, I've been in this hobby for decades so have gone through multiple new speakers.  The break in time among those varied, but it was minor with the SP-888s I bought new last year.  They were not demos bu in factory sealed boxes.

The break in was very slight, nothing like you described.  Mainly a tightening of the bass and a bit of solidifying the detail and imagining.  Change was slight and seemed to have settled in after 30 hours or so.  In fact early on friends who heard the speakers remarked on the excellent sonics, including bass.  I'm very pleased with mine.

Worth noting that break-in times for new speakers can vary widely but amount of time played and volume played at are always two key variables that go into it.  Amplifier used can also make a difference in that some amps may work a speaker much harder than others.

Saying it takes a certain period of time alone for a speaker to break in is meaningless.  Based on what?  Some may even sound their best right out of the box.  

It all depends.

To quote the head monk from the Kung Fu tv series, “ Patience Grasshopper, patience”. 😌
Enjoy the music. 

I had the same experience with my SF Il Cremonese. Out of the box they were nice but were restricted in their low end range and dynamics. A massive difference after a few weeks of run time - in extension, smoothness and dynamic ease. 

Bought a pair of Dynaudio last year. Same experience. Was initially disappointed. Talked the store owner and he recommended 300 hours of break in period. Thought 100 hours would do. Nope. It took 300 hours to get the full performance. Very pleased now!