@rifraf4u and others.
I was once a break in denier. I’m pretty pragmatic and I dont get too emotional one way or the other. In short, Im not invested in any particular camp. There are multiple explanations, some of which may or may not be measurable.
Electronics and tubes. These are thermal in nature and vary in duration. If you dont believe in it, thats cool. You have to admit that if you place a piece of gear in your system new, straight out of the box then it will sound better once its warmed up to operating temperature right. Well certain parts reach that temperature more slowly and retain/dissipate heat at differing durations. I’m not a believer in hundreds of hours being necessary for the gear to reach equilibrium but its real.
Speakers need breakin. It might take minutes, hours or days depending on the physical properties of the drivers as well as the type and complexity of the crossover components. Additionally, most home users dont break something in at sufficient volumes for a sufficient duration. Its tough to push enough voltage or current for sustained times that accomplish the task. Thats why one user reports that they sounded great after 10 hours while another may say 100. What temperature is optimal vs what is the ambient temp vs volume and type of breakin track. I was told by a dealer I trust that a pair of speakers I had needed 500 hours. After about that long, the speakers still sounded marginal to me. I admit I dont play loudly and I just cant imagine why that wasnt a sufficient amount of time. Skeptic that I am, I chose to go in a different direction and the dealer took them back. They broke them in for more hours and are thrilled with them. I believe in speaker break in because there is no way anyone with ears would have tolerated them otherwise. Similar electronics in my system as the new owner. My bad.
Cables, most of us dont pump enough voltage through them to break them in sufficiently. I thought it was voodoo. I bought a cable cooker to see. I had multiple sets of interconnects, cooked half of them, placed some in my system. Started with one channel of my system and had a friend install them with me out of the room. One channel from source through the amp and then I came in and listened. It was apparent from the first note, one channel sounded much better and the other much worse. One channel was playing with more ease, dynamics, tone and texture that I was pretty certain something was wrong with installation or gear adjustments. The next test/validation was a trick on me by my friend. I installed the complete set of cables that had been cooked and left the room to go to my garage to get something, came back to my listening room and we began to listen. Immediately I was struck by the fact that one channel was sounding bad in comparison. I began checking connections and shut down the system to check tubes, etc. He then burst out laughing…while I was out of the room, he had switched one channel back to uncooked cables without my knowledge.
Now, you can believe its real or not, doesnt much matter to me. Im not into tweaks, you wont see cable elevators or contact enhancer or funky fuses around my place. Breakin is real, the sufficient duration though can be debated.