JBL 125A voice coil rubbing

[martinle]

I am re-foaming jbl 125A speakers.
One is already finished and it is perfect (there is no friction when raising or lowering the cone)
The second already has the new foam attached to the cone (but not yet to the basket) I am holding it with many "tweezers" to do the tests before sticking it.

the thing is this: it seems perfect when you move the cone down, but when you move it up it always rubs. This happens with any method of centering (battery, 30 Hz and manual).

The speakers (the boxes) are not "sisters" they have different serial numbers among other things, so they may have had different "care" and are not in the best condition.

any ideas?

I think the voice coil is made of paper and could be in poor condition from having been stored in damp places.
open the dust cover and see what happens? can be detached with toluene instead of cutting

thanks and sorry for my english from google translate

[short_circutz2]

I am re-foaming jbl 125A speakers. One is already finished and it is perfect (there is no friction when raising or lowering the cone)The second already has the new foam attached to the cone (but not yet to the basket) I am holding it with many "tweezers" to do the tests before sticking it.the thing is this: it seems perfect when you move the cone down, but when you move it up it always rubs. This happens with any method of centering (battery, 30 Hz and manual).The speakers (the boxes) are not "sisters" they have different serial numbers among other things, so they may have had different "care" and are not in the best condition.any ideas?I think the voice coil is made of paper and could be in poor condition from having been stored in damp places.open the dust cover and see what happens? can be detached with toluene instead of cuttingthanks and sorry for my english from google translateDid you try using shims to center the voice coil?

[martinle]

not yet... will be the next thing I try.
what catches my attention is that the problem only exists by moving the cone up/out...

[edgewound]

not yet... will be the next thing I try.what catches my attention is that the problem only exists by moving the cone up/out...The original 125A voice coil former is Nomex. The 125A magnet is also prone to demagnetization, which non-trivially affects the damping and frequency response of the driver. Over excursion is a symptom of a weak magnet.So...Two things could be causing the voice coil rub. The voice coil former could be bubbled due to overdriving, which can also cause demagnetization...Or the end of the voice coil former is deformed from bottoming out against the rear of the motor housing or hanging up on the pole piece from extreme overexcursion. Deformed end of voice coil can possibly be fixed. Bubbled voice coil former is done...must be reconed. Best to do them in pairs if reconed with reproduction parts due to the difference in DC resistance from OEM...Or try to find a single replacement with OEM parts.Best of luck on your search.

[martinle]

"edgewound" thanks for your answer. In my first message I try to explain that I am in the process of refoaming (edge glued to the cone but not yet to the basket. I hold this end with tweezers after centering it) I make the excursion of the cone with my hands as a test.

I'm inclined to think that the former end of the voice coil is deformed. Probably due to excess humidity as well.

I'm going to try to peel it off with toluene. First, the dust cap and see and test with shims. And if it doesn't work, I'll try to take off the spider with toluene and check the coil. I just have to find a ventilated and warm place in the middle of winter... not so easy the latter

thanks again
Saludos, Martín

[martinle]

Today I had some free time... So, I took off the dust cap and tried the centering with shims (I don't understand why it only talks about cutting or not cutting) I keep getting the same result... the magnet works well, it is still strong. onedrive links because i have not had success with the Manage Attachments: Photos https://1drv.ms/u/s!AjqaoTc3kOo7glDZXklzg-QzP-gh?e=oZ5jMv https://1drv.ms/u/s!AjqaoTc3kOo7gk2cftWxSwfV9jQZ?e=5tvbXoa video with the problem: https://1drv.ms/v/s!AjqaoTc3kOo7glYOhs44c0UAEonu?e=4yAbqq