Tweaks break-in period ?

First, thanks to all for your answers. But, I feel necessary to add the following informations.

To Argent: Maybe molecular structures could-in fact- only be altered by extreme temperatures but what happened reminded me of the differences one can hear between a brand new interconnect and an identical one with several hundred hours of burnin (playing music). I can clearly hear the differences when A/B ing them and we still are not talking about extreme temperatures. So, maybe what's happening is similar. I have no idea.

To Albert Porter: I didn't move the interconnects, the power cord or anything else nor did I turned off the power amp. If I would have done so; me or one of my fellows would have noticed and that is why such a difference stunned us all. The only thing I had to do was to lift the amp I'd say to less than 1/4 of an inch...

To Bluenose: As you see I didn't move a single wire. All my cables are suspended and not crossing each other. I (we) certainely can't see how I would have disturbed the balance. And, being a Canadian from Montreal I certainely know about canadian beers...but it was not one of those night... ;-)

To Flex: My amp is marked with little dots (stickers) underneath it in order for me to put my tweaks at the exact same places. As you said, small changes in position of tweaks can make an audible difference.

To Bob Bundus: We did the "sanity check" i.e reverting to the original cones and vice versa with always the same results with the new set: a harsher, thinner, more up-front and less musical (coherent) sound. A little (very little) sibilance was also notice.

To all: Again thank you for your comments. With the new details I just gave the question is still valid but I am starting to wonder if a mistake could have been made at BDC i.e maybe a pair of MK IV were marked as MK III ?

Best regards,

Marc-André Rodrigue

To Tacs: I (we) was not expecting anything. As I had a new set, it was time to give my friend his set back and replace it with mine. That's all.

I find your other points interesting as we tend to expect sound differences when tweaking. Still it was not the case this time. On the other hand, we might have been distracted from the music because we were -in fact- settled into a bliss. Interesting theory. I just guess we were distract big time then.

I thank you for your intelligent comments you had (and have) me thinking ;-)

Best regards,
Marc-André Rodrigue

Cornfedboy: Thank you for your positive feedback...it was exactly the kind of answer I was looking for...the toaster thing could have been helpful...but I already tried it and found that the difference was more important in the lower midrange (more delicacy) especially on track 5 of Ottmar Liebert's Nouveau Flamenco...

Please let's respect and not ridiculise each other. I was just sharing an audio experience with you all. Isn't it one of the main reasons why audio forums like this one do exist ? That being said, I still have a good sense of humor...;-)

Respects,
Marc-André Rodrigue

marc: i meant no disrespect and thank you for your ackowledgment of my mere attempt at humor. i do, in fact, applaud your enthusiasm in finding yet another pathway to better sound. -cfb

Corfed. your post WAS funny...thanks again.
Tacs, I think you nailed it: expectation bias hoodwinking!