Speaker Break-In - What Physically Changes During Break-In To Enable Better Sound?

I have no way to prove any of this, but I "believe" that after listening to my speakers for awhile, they sound better after 30-40 minutes or so than they did at the beginning.  Perhaps the drivers become more compliant (?) or warm up a bit.  Whatever it is, the sound seems to fill the room better, the stage opens up a bit more, and the music becomes more involving.  As for break-in of brand new speakers, the crossover certainly may undergo some changes, although one could argue that certain manufacturers do test runs of new units at the factory to rule out any problems before they ship them out.  But as it is with my present system, with the preamp and amp already in "standby" mode, I have to believe that it's probably the speakers that go through a warm-up period.

The capacitors, resistors, inductors, internal wire, solder joints and binding posts. Capacitors alone take up to 500 hours to sound their best.  

Like kosst_amojan said, the diaphragms of speakers are stiff "out of the box." In my experience, shipping in cold weather will make them stiffer (or reverse some of the break-in); and full-range drivers seem to require more break-in. Complete break-in for some drivers require many hours and even weeks and months depending on how much they are played.

Physically you get older!!  I think it is a combination of our getting in tune with the different sound and I am sure what grannyring pointed out. And I strongly feel my system which is solid state sounds better after about 20 minutes playing. Could be just me thinking that though and it is not really happening. 

It all depends on design. Big motors and acoustic suspension will dominate response on high quality drivers - spider and surround compliance being negligible. On low quality drivers then you can fully expect the manufacturer to recommend a break in period - this is because the response of poor quality cheap drivers will be affected by minor things like spider and surround.

On high quality speakers the drivers should be ALREADY broken in by extreme stress testing like in these two test examples (especially watch the second test on a small driver which is totally extreme)

https://youtu.be/ZEBICv7QPDM

The following video shows how drivers are built and individually tested from the ground up.

https://youtu.be/HJHul8HgbPs


Many speaker manufacturers are simply using mass produced OEM parts often they don’t even run multiple tests except a go no go (it works or it doesn’t). Mass produced parts produced for a large market of speaker builders are designed to be easy to build and reliable with low reject rates. This means performance and tolerances are much looser with design considerations weighted towards reliability and ease of manufacture rather than pure performance. These speaker manufacturers may indeed recommend break in as parts may not have settled thermally and mechanically....having never been tested thoroughly until you receive your speaker.