I guess I'm still confused about this whole break in thing. I personally think it does happen, especially to things that have moving parts, like speakers.
I've also heard it happen, or think I have heard it happen.
Some items in the quoted article I'd like clarification on if possible.
The author states:
"When a newly-minted driver rolls off the assembly line it will typically not measure or otherwise perform as one of its well-broken in siblings does. In large part these differences arise owing to the fact that said driver’s spider (often crafted of a varnish-impregnated linen) is not as compliant as it will become once it’s broken in properly. Depending on number of mechanical factors relating to its design, construction and materials composition, a net post-burn in compliance increase on the order of 5% - 10% would not be unusual."
So, he clearly believes that speaker breakin does occur.
He follows this with some textbook math. Then states:
"Required break in time for the common spider-diaphragm-surround is typically on the order of 10s of seconds and is a one-off proposition, not requiring repetition. Once broken in, the driver should measure/perform as do its siblings, within usual unit-to-unit parameter tolerances."
I agree with the first part of this statement, initial breakin happens in a fairly short time if done as he suggests- with a signal that fully stretches the spider and suround. I'd says perhaps in a minute or two. After a couple of minutes of burnin a raw driver is ready to be measured. Obviously the details will depend on the driver but a few minutes of being fully stretched should be enough. But, I think the process does require repeating. The spider and surround can both reset themselves (the material on the spider - do they still use varnish? - can reform itself, and the compliance of the rubber surround will also reset. So, until the "initial beakin" has been performed many times you have to repeat that initial breakin procedure before valid measurements can be made. Does the articles author agree with this?
The author then goes through a series of simulations assuming
"The post – break in specs are derived from a 5% increase in suspension mechanical compliance." If I understand what has been done he has assumed a 5% change in raw driver compliance and plugged it into a textbook speaker designing program. All very interesting, but if speakers could be designed by textbook to sound good we could all save ourselves alot of time listening to different speakers to decide what we like. . .
Certainly there is more to speaker design than frequency response, or am I just being silly?
next the author states
"The compliance of the air enclosed within the enclosure is significantly less than the driver’s suspension compliance, therefore the enclosure has the dominant influence where it comes to determining things such as system resonance." This totally confuses me. If true why do even consider the free air response of a raw driver? Sure, the compiance of the air in a speker cabinet is very important, but is it really dominant? I know that temperature, humidity, and pressure can significantly effect the role of air in speakers. Maybe speakers should be designed for specific altitudes and climatic conditions and use the cheapest drivers if the air plays the dominant role?
I wonder, if I take a sealed cabinet speaker to a different altitude and temperature how long does the air inside take to break in?
Finally the author gets down to what may be the salient point,
"Regardless of how completely broken in a driver may be, while under operating conditions many well-known & understood mechanisms come in to play that affect several of a driver’s measured parameters, including suspension mechanical compliance.
When under normal operating conditions, its not at all unusual to see in a driver that has already been broken in a further 5% to 20% drop in a , due largely to an increase in the mechanical compliance of driver’s suspension. In this case, typically it’s the temporary elastic deformation of the surround that’s the cause of the increase in driver compliance.
Cease stimulus and the driver’s compliance will return – in most cases within seconds or minutes depending upon surround design, material composition, ambient temperature and so on - to its pre-stimulus value; the compliance changes are temporary. So too are the changes that occur in all the other driver parameters that are effected by compliance, hence the changes in , etc."
What is not well understood in my opinion is how these changes in raw speaker performance change with a driver that is "well broken in". And how long it takes to reach this stage. Is a few 10's of seconds at near full extension enough? Does this have to be repeated many times? Is there a difference between breaking in a driver quickly at near full extension at the resonant frequency in free air and using smaller excursions at a variety of frequencies in an enclosure? Is 10's of seconds enough for all drivers?
What is not addressed in the article are the possible effects of speaker cone breakin. I wonder what these might be in a cone that did not "sport titanium diaphragms"
Maybe 10's of seconds of break in at near full excursion of a raw driver really is equivalant to 10's of hours of normal listening with a driver mounted in a box? I don't think so, but could be wrong. All I know is I will not judge a speaker until it stops sounding differently - sometimes that takes longer than I would expect.
The breakin thing is real, as noted by the author of the linked article. What is not clear is how long it takes, and what path it takes. Though not stated, one thing is clear, break in is the first step to break down. I suspect that break in and break down both happen fairly quickly in the liftime of a speaker. It is the in between time that we hope our speakers will spend most of their time. There is no doubt that our ears/minds also adjust. How much of the difference is due to speaker changes vs mind changes has not been determined and probably varies. . . My 2 cents
