Do you think driver “break in” is real?

Do you think “high end” drivers and crossovers typically need a “break in” period before they sound their best?  I ask because, I believe I’ve experienced this first hand in a very significant way. I replaced the tweeters (same exact brand and model as original) in my ACI Sapphire 25 year anniversary edition speakers and for the first week I thought I’d lost my all time favorite speakers. I was depressed!  So I just kept playing them…  finally after a couple weeks, I’m literally stunned and blown away at how incredible these speakers sound. Completely different than the first 30 or 40 hours after I put in the new Scan Speak tweeters. So I say break in period must be real - at least for some drivers. Has anyone else experienced this to a degree that is unmistakeable?  
Crossovers too?  I just rebuilt the crossovers for a pair of ACI Sapphire XL’s (using highest quality components- same values) and so far they sound mediocre. Hoping for the same result as my other Sapphires but after about 20 hours - no noticeable difference - and they do not even sound as good as prior to crossover rebuild. They sound flat, too bright with poor imaging - but for 10 to 15 years they were pretty great sounding speakers. Thoughts on crossover break in?? 
Thanks to anyone who responds!!  


I'm convinced it's real based on the mechanical explanations I've heard.

In my own experience, it's hard to tell because simultaneously while drivers are breaking in, my hearing is accommodating to new sounds. Where the adjustment in my ears lets off and the adjustment in the drivers begins is very very hard to tell. There's no control on this experiment and auditory memory is weak for detail.

I have rebuilt Xovers many times each capacitor sounds different 

foils are normally better then typical poly sprayed particle conductors

go to humble homemade hifi capacitor test 

Duelunds copper foil oiled paper being the finest ,and can take up to 4-500 hours or more to fully runin ,, resistors  path Audio are far better-then the typical ceramic type.sonically and accuracy , inductors copper foil for tweeters midrange are far better then these cheap sledge hammer wire over a iron core ,for bass a big awg 12 or 14 guage open copper core are preferred , all these parts are much more expensive but dramatically increase imaging soundstaging and musicality.

as far as drivers absolutely mechanically the surrounds have to loosen up the wire has to stabilize as well as other mechanical parts of the drivers ,I give it at least 200 hours playing at increased volume levels , I use Isotek excellent runin cd ,and track 3 tune up track for years. I have over 20 years at this and owned a Audio store for a decade.  

Put on a new pair of jeans, or shoes.


not so comfortable. After a couple of days of use, they get better. 


Break in is very real. As an avid DIY builder of audio gear, it’s obvious to me how much benefit a driver will have from  break in over time.

As a similar analogy, consider a new automobile engine: There’s a reason you’re not supposed to over-rev the thing until so many hours have passed.

i agree that break-in periods are difficult to empirically evaluate due to our familiarization with the sound over hundreds of hours.