Driver Break in - Fact or Fiction?

[Ricci]

That's a great post Kevin. I recently read a thread where a guy was apparently having his vc's break in. He said the dcr dropped substantially. I've never heard that one before and I'm not sure what to make of it. I definitly don't believe that is actually what happened. I just don't see how it could be possible at all.

[Kevin Haskins]

Nahh.... it will change with temp. He may have measured them directly after running them and got a high DCR and then did a measurement later, after break-in, and the taken the DCR after the coil had cooled. That would show the change you are describing.

The DCR is set by the copper or aluminum length/diameter and obviously that is a fixed parameter. The impedance sweep can be changed by acoustical loading and break-in, enclosure shape/size & obstructions but you don't see any difference in the DCR.

Kevin Haskins
Exodus Audio
www.diycable.com

[Bill Fitzmaurice]

Kevin Haskins wrote:

There doesn't seem to be any credible research showing that cones break-in after a given period of use either.

They don't, but in the case of paper pulp cones their mass, and therefore Mms, Fs, Qes, Qms and a half dozen other parameters, is affected by the humidity in the air. If you think your subs seem to go lower in the summer, when average humidity is higher than in winter, they probably do.

I recently read a thread where a guy was apparently having his vc's break in. He said the dcr dropped substantially

DCR goes down when coils are cold. That's why superconductors are supercooled. The increasing DCR of a coil when heated is the source of thermal power compression.

[Kevin Haskins]

I live in the Pacific Northwest, my subs go lower year round.

Kevin Haskins
Exouds Audio
www.diycable.com

[ISLAND1000]

Then as global warming continues the best driver performance will be had at the "poles" both north and south it seems . . . . . except for "hysteresis" and the effects of the Van Allen radiation belts.

[kryptonitewhite]

YouTube - Maelstrom-X

I have been breaking in my subs for years, and have frequently noted something that happens in this vid....

When I start, i bring the driver to it's point of mechanical discomfort... always freeair of course. Once i reach that level, I do not back off only a notch!!! I back off several, because as you clearly hear in this video, the driver breaks in and achieves a higher excursion with the same level of input. I break mine in over several hours in a room that I will be in for the whole duration, and sometimes I have to re-back down the input level multiple times as it begins to over excurt slightly as the compliance decreases.

EDIT

I re-watched the vid, and noted there could be a few misunderstandings, then I scanned through this thread further (I didnt read the whole thing) and noticed there are other vids

Anyway, I noted:

up until 17 seconds, it is playing at low level, then he begins adding input...and it needs to be noted that the repeating track is increasing in frequency, generally excursion should go down as it gets higher. Would have made for a better example if it were a constant tone.

at 24 seconds the first hint is easily heard of nearing limits, then continues to increase... while increasing input as well?

35 seconds is the clear point of overexcursion

at 46 you hear it again, and he notes it, and backs off... but i believe he leaves it?

at 57 it overexcurts again... was it at the same input level since after he backs off at 46 seconds??

as a rock guitarist, i can assure you you DO need to break in speaker drivers, i've blown thousands of speakers up over the last 40 years or so...

if you break them in they seem to last longer and take more abuse...granted, i'm dealing with a situation where i'm LOOKING for distortion ;P

we used to take speaker cabs, hook up an amp and feed a guitar back overnite at a low level...
those abused speakers seemed to function much better.

so i would suspect breaking in a driver, much like anything else, would be wise.
peace

[Ricci]

That Mal X is not too happy at a couple of spots in that video. Sounds like either spider slap or suspension bottoming. Too bad the video is a low resolution it's hard to actually see what's going on with the driver or what the excursion levels are (looks pretty high). The Tempest X never exhibits a noise that harsh in it's video. Maybe it overloads in a bit nicer way.

IMOP the best way to break in any driver is to just use it the way it is destined to be used.

[kryptonitewhite]

can you even bottom out those 18" 06' XXX's?
3000 watts 30Hz on up, disgusting er scary?

[Ricci]

I was told by the senior RE tech that the suspension is fully stretched at about 63.5mm one way. The vc's would hard bottom somewhere past this point but something on the suspension would have to break first. The suspension starts to tighten up a lot once you get to the ends of it's travel. It would probably take in excess of 1000watts of <10hz material free-air to physically damage the driver.