Component Break In. Truth or Fantasy

So way back around 1977, I was a young man living in a mobile home with three other guys, up in Northern Alberta.  I didn't have a stereo and I didn't have any money to buy one.  But I had a used cassette deck from someone's car, and a couple of very cheap 6 inch speakers.  Again, out of a car door.  Just for a lark, I mounted those speakers in a couple of 8 cube cardboard boxes (that's 24" x 24" x 24" for those who have never moved a house).  Used basic lamp cord as speaker wire.  Not surprisingly, the sound was not very good.  But here's the thing.  After a couple of weeks, we were so accustomed to the sound, we all thought the "system" actually sounded pretty damn good.  So did the lamp cord "burn in"?  Did the speakers "open up"?  Did the cardboard boxes go through a molecular transformation?  Or did our brains simply become accustomed to the sound that was now perceived as being more than adequate.  This is absolutely a 100% true story, and IMHO, speaks volumes on the subject of equipment break-in.

Why is it that when things are supposedly broken in they always sound better? The odds of that happening are basically nil, yet we read about it all the time despite no objective evidence that it's real. The faithful (emphasis on faith) will go on and on about it, but it ain't happening.

Besides, manufacturers "voice" their equipment to sound a certain way so if it changed after x number os hours of use, that would make no sense and not be what the designer wanted. 

Read this post at an opportune time having connected a brand new streamer dac  two days ago. It’s a Lumin D3 and it has been running continuously since. First impression was that the sound was exaggerated on the high end, harsh and just bad. Right now I am streaming Katy Lied through Roon and Quboz and it sounds much better…fuller and more analog round but still not as nice as the D2 it replaced. Hope to hell it keeps getting better.

Anybody who has ever modified or built equipment, while taking the time to carefully and critically listen to how various part choices contribute to the sound, knows quite clearly that parts change in sound over time. Let’s take for example one part used in equipment - capacitors.  It becomes completely obvious to the listener that cares that these capacitors change in sound over time.  This is rather obvious. Burn in does not always cause a part to sound subjectively better to the listener or builder.  I have used capacitors that ended up sounding A bit too tipped up in the presence area for me to enjoy long-term after burn in.  When building cables, modifying gear or building gear I always wait for burn in  before seriously evaluating the finished product.  Doing it any other way is folly.  
 

Obviously, the gear we all enjoy contains many more parts that also require burn in beyond capacitors. Folks, even the vacuum tubes in your tube gear is known to sound different from hour one to hour 60. Of course burn in is real. I can hardly think of anything in this world more real. The only way one could ever know this for themselves is if hey were to give it the due diligence required to hear the sound differences. It requires a discerning ear as well as the passion to actually give it your sincere time and attention.  Not everyone cares equally about such distinctions in sound quality.  

I see a lot of confusion btw burn-in and break-in, here is AI definition, which I agree with:

• Burn-In: This is a process used primarily in electronics where components are tested under stress (elevated temperature and voltage) to identify early failures. It helps ensure reliability by weeding out defective parts before the product is fully assembled and used.

• Break-In: This term is often used in the context of audio equipment, particularly headphones and speakers. It refers to the gradual improvement in sound quality as mechanical components settle and adapt to use over time.

I design analog circuits, mostly to use in large, 1b+ gates SoC (system on chip). SoC manufacturing has a burn-in (accelerated aging) step. Accelerated aging requires to stress key spec parameters, such as temperature, increased voltage, frequency., etc. All these steps are included in design process, and verified by extensive simulations. Devices in circuits used with small margins to max allowed conditions are aging faster than devices in relaxed usage conditions.