I have been playing around with various SB Acoustics 5" mid-woofer drivers in a 3-way design. I have noticed a subjective change in the NRX (pulp/CF) cone version after a few weeks constant use. I am now auditioning an aluminium cone version. Should I expect any audible break in-change? The spiders and surrounds look identical.
I should think "break in" applies to the front and rear suspension rather than the cone material.
The Wikipedia page on work hardening
https://en.wikipedia.org/wiki/Work_hardening
contains these quotes.
"Some materials cannot be work-hardened at low temperatures, such as indium, however others can be strengthened only via work hardening, such as pure copper and aluminum."
"Devices made from aluminum and its alloys, such as aircraft, must be carefully designed to minimize or evenly distribute flexure, which can lead to work hardening and, in turn, stress cracking, possibly causing catastrophic failure."
So it is confusing whether aluminium work hardening is beneficial or detrimental to cone performance.
https://en.wikipedia.org/wiki/Work_hardening
contains these quotes.
"Some materials cannot be work-hardened at low temperatures, such as indium, however others can be strengthened only via work hardening, such as pure copper and aluminum."
"Devices made from aluminum and its alloys, such as aircraft, must be carefully designed to minimize or evenly distribute flexure, which can lead to work hardening and, in turn, stress cracking, possibly causing catastrophic failure."
So it is confusing whether aluminium work hardening is beneficial or detrimental to cone performance.
I think the key word here is "subjective". I should like to see some objective evidence of loudspeaker "burn in".
If your driver's characteristics change after a few weeks, then why wouldn't they keep on changing?
If so, at which point in time could you say that the driver is fully broken in and sounds "right"?
We're probably talking more about psychology than metallurgy! 😉
Almost all of the SB Acoustics extensive range of woofers, mid-woofers and mid ranges, have the following statement in their datasheet.
"IEC 268-5, T/S parameters measured on drive units that are broken in.".
This includes aluminium, ceramic, carbon cones. Maybe they know something.🤔
"IEC 268-5, T/S parameters measured on drive units that are broken in.".
This includes aluminium, ceramic, carbon cones. Maybe they know something.🤔
At SEAS they told me this : woofer break-in takes 2 minutes with 20 Hz sinewave at Xmax. I think they know their stuff too.
So we agree. Break-in is a "thing". Maybe 2 minutes at x-max equates to a couple of weeks at normal levels.
No reasonable diyer is likely to use the SEAS method on their new expensive driver.
My original question was whether the cone material is involved or is it just the suspension?
No reasonable diyer is likely to use the SEAS method on their new expensive driver.
My original question was whether the cone material is involved or is it just the suspension?
Probably when the T/S parameters are stabilised after a given interval of consistent operation.
Like the reported 2-minutes at x-max SEAS approach.
My impression is that metal cones don't change over time. I've measured 15 year old SEAS Excel magnesium drivers, and they measured exactly like new.
20 Hz would work the suspension and warm it up, with the forces being distributed in a way that's peculiar to 20 Hz. But if you apply 2kHz or some other frequency, the mechanical wear and tear would have a different distribution. So if the cone does indeed harden, like with aluminium, I'd probably go with what some others recommend, e.g.: 100 hours of music at low volume, and gradually increasing the level.
Hardening is only relevant when a material contacts a harder material...air being quite soft does not care what the hardness of an aluminum driver is.
What Galu says in post #2. For best performance slow gentle break-in so as not to impose a memeory (in the spider in particualr).
I do expect that cone to evolve somewhat as the metal moves.
dave
I do expect that cone to evolve somewhat as the metal moves.
dave
Counterexample: Mark Audio Alpair 10.3. It gets better over as much as 1,000 hours.
dave
They sound better. More bass. More detail. Smoother. The middle one the most importat and still not really measureable.
dave
dave