Driver breakin period, what’s the science?

Almost all the break-in occurs, at reasonably loud volume, in the first 5-10 minutes. If you still hate them after that period of time, then you hate them, though keeping them will cause your brain to change far more than the speakers.

However, changes in mechanical compliance of the structure can keep occurring for 5-10 hours. After 10 hours, not much.

Relative output of your driver's did not change more than a fraction of a db after the first few hours. The crossover points may have changed a very small amount. The l-pads and tone controls were not doing what you think they were.

the better the speaker and the more resolving the system is, the more this can be noticed, happens over the first 100 hrs at least... for mine, changes were noticeable up for 300-400 hrs...

this is significant... those who say no just don’t know...

One of my business partners would beg to differ having done extensive work on cone materials and cone breakup which required extensive testing of drivers to determine where parameters stabilized including high speed surface imaging and laser interferometry.

So have these new speakers and been told they need a hundred hours to be broken in, and then sound will improve.

This statement above is total crap. It does not take 100 hours to "sound good". There will be subtle changes after hours of reasonable volume. No magical major improvements after that. The only thing that happens by 100 hour is you got used to them.

w.r.t. Capacitors, electrolytics if they have been sitting can have a parameter change over a period of time, mainly in DC parameters, but you don't see those too much in high end speakers. Film capacitors are very stable ...it is why they are used. There are people who have equipment and can test these things to significant accuracy. They are not the people making the claims. We can't measure how humans will perceive change, but we can measure if there is change.

Alan Shaw of Harbeth will tell you it’s bogus and a phycological effect,

There's a nice article on driver break-in at the GR Research site complete with measurements of various drivers as a function of time. 

I have no reason to question Danny's numbers and I know my colleague has had some discussions with Danny over the years, I think they even defended each other on this topic on a forum once.


It goes back to the ops questions,

"So have these new speakers and been told they need a hundred hours to be broken in, and then sound will improve."

... whoever told him this was out to lunch. They don't magically improve after 100 hours. The major compliance "issues" work themselves out quickly, i.e. the distortion will drop quickly. After that, the driver has predominantly settled in 5-10 hours. After that, it will be subtle changes and more so on the bass. The changes in the other speakers, i.e. crossover points, etc. would be within the tolerance of manufacturing.

w.r.t capacitor break-in, I would challenge anyone to show any measurements of a film capacitor that shows parameter changing greater than the part tolerance ran at the typical volts/current in a speaker.  Don't say "well we can't measure" ... We can't interpret how humans will respond to the measurement, that does not mean we cannot measure changes.  Some capacitors are not well made and susceptible to absorbing moisture, and could change with humidity / temperature. Well most will change with temperature to some degree any way.