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!!  


@erik_squires  Exactly. Within minutes. Certainly not the "break-in" that people talk about or need to worry about. Several custom speaker builders and kit makers have run this test on drivers so they could get accurate "broken in" specs. I read the first one about 20 years ago. I believe it might have been a kit maker whose name escapes me, but it began with a 'Z'. I believe they shut down years ago. Another who did the measurements was Bill Fitzmaurice.​​

Part of the myth is so you won't return it immediately and you'll get used to the sound of your new speaker

I can't imagine getting used to a speaker I don't like. I can imagine a speaker growing on me though that I like from the moment I hook them up.

there is no way I would argue a point that most people believe as it sure won't change anyone's mind.  Whether it happened or not, my stuff never changed in sound if it did.

Absolutely real. I once had to replace the diaphragm on one of my previous horn tweeters; well the fixed channel was harsh and piercing for a couple days, skewing the stereo image to that side, until it settled down and both channels started playing equal.

Same with my new tweeters, I had to change the crossover settings after a few days because they started really hot and bright fresh out of the box and ended up smooth to the point of dullness until I changed the settings again.

@willywonka come on... it's one of the easiest things to verify. 

Just put in a brand new tweeter on one side, and keep the old, used tweeter on the other side, and see if you can get any decent center image. I guarantee you won't! And you can do the same with most everything that has a break in period, like capacitors, or even cables, you will get the same results.