Thank you for the logical explanation - makes sense in this particular case for Stax headphones. My experience with speakers (bespoke Kudos, Neat, Naim, Linn) is that all purchase drivers from a supplier (frequently SEAS), cabinets from another - and simply serve as the final assembly point (well they also did design them). None of them put any significant hours on the speakers prior to shipping. Since the drivers are "moving parts", internal wiring needs to come up to speed, internal crossovers with their components (caps etc.) the same, hence "break in" for speakers (at least the one's I am familiar with).
Electronics - Naim - notorious for break in. Easily a month - and for general usage must remain powered up 24/7. Why - who knows - thats just the way it is. Break in - love it or leave it.
Thanks again for the Stax explanation - and sorry for the two channel digression.
Now time to sit down and listen to the 009S and compare. Only problem - handicapped by a 353XBK.
A big handicap????