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!!  

sal1963

Drivers measurably break in. Some makers specify whether the specs are broken in or not. That is, they’ll say something like "measured after 100 hours..."  Typically this is for woofers and mids which can have noticeable drops in the driver resonance frequency. 

I’ve heard caps break in with very weird, surround like effects until they settled in.

Yes, absolutely. The driver cones are very stiff to start and are designed to flex with the output a bit over time. Usually this takes anywhere from 100 hours to 300 hours to sound best. 

Most crossovers have capacitors that also need approximately 50-100 hours to break in, as well as some time for electrons to flow through any coils.

100 hours seems to be a pretty sweet spot to gauge how something is going to sound, but I’ve heard both drivers and electronics take anywhere from 50-400 hours. My tip for break in is to run Brown noise loops continuously on low volumes, even overnight. They are a bit softer on the highs and will pose minimalrisk on frying tweeters. 

In short, BIG TIME.

I recently bought a a high-end MOON streamer DAC . The manual specifies a 400 hour run-in time for all the build components to properly set.