breaking in without voltmeter

[Gregory East]

I downloaded trueRTA free version for the signal generator and got it hooked up through the stereo to break in my bp102.

I have it sitting on the carpet cone up at 25 Hz. No voltmeter but enough power to make it move. It's pretty well silent. Salt goes apeshit though.

It is very hard to make out the amount of movement at the back where the cone meets the next bit (what's that called?) Nothing to focus on. I guesstimate about 1mm travel.

Enough juice?

[Gregory East]

Nabbed this BF post which was in response to someone breaking in 12's and 15's

mainly go with eyeballing the cone, looking for about a quarter inch of peak to peak excursion. 8 to 12 volts is the usual requirement. I've measured differences in Fs as much as 20Hz before and after break-in, though 5-10 Hz is the normal range.

So how much for 10's?

Edit, so I have bumped it up to about 4-5mm. Measured by having a white background to tape measure/cone.

Pretty sure the smell is from the amp not the driver but going back to sniff now!

[LelandCrooks]

4mm is plenty. Xmax for that driver is 6mm..

[Sydney]

I see a tendency to treat driver break in 2 ways:
A blanket method applied to all drivers, and/or a precise method.
Since not all drivers have the same Fs and xmax limitations. I personally would not use a specific frequency, at a specific voltage level, for a specific time, for all drivers.
I tend to go easier ( cone barely moving - a mm or so ) and in the past I've used filtered noise and just let it go and come back later.
Umm... What's that smell? Hopefully new amp.

[James R]

I tend to go easier ( cone barely moving - a mm or so ) and in the past I've used filtered noise and just let it go and come back later.
Umm... What's that smell? Hopefully new amp.

This is the way a friend of mine does it( without the what's that smell) he does speaker reconing amongst other things

[Gregory East]

So far so good. I was using Bill's recommendation of 10 Hz below Fs for max wobble with minimum power. (35Hz Fs for bp102). The smell was the old hifi amp that had gathered dust for many a year until I brought it out of retirement.

I backed off the power a bit in case it loosened up significantly overnight, just as well as it was doing 4mm.

Is x-max middle to outside or inside to outside? I thought it was the static to edge so 12mm overall before it would be breaking something to pieces as opposed to breaking in.

I've bumped the juice down some more so it's down to 2mm wobble. I gather there is no general agreement on the max wobble as a proportion of xmax.

[Sydney]

This illustration agrees with most definitions I've seen :

and from LDC: Xmax = amount of voice coil overhang

[bgavin]

This is an excellent visual, but it fails with underhung voice coils such as the JBL K145. At that point, it is up to the reader to understand that Xmax is the amount of travel where the number of coils in the gap remains unchanged.

Underhung coils are quite rare these days, due to the expense. Making a big magnetic motor to fully surround a shorter coil is an expensive proposition.