I have now run across a 2nd driver that was reconed with authentic JBL recone parts that have a problem with intermittent voice coils.
The 1st time it happened, the recone (E-130) was done by a expert with JBL drivers and the problem did not show up for him as he was running SS amp to break them in for me. I use tubes which have no DC offset and no current flow at no signal condition. I say that because the problem will not show up if you have sufficient current through the voice coil which seems to jump across the very small hairline crack in the voice coil windings.
I would be listening to the drivers with music playing and all of a sudden it would just quit playing like you disconnected the wires leading to the drivers. Since I use tube amps with output transformers, I took a 9 volt battery and tapped the driver terminals checking for continuity(DON'T do this with SS amps!!!) and after I heard the driver click with the battery connection the music resumed playing again. It would quit again after 10 - 20 minutes and I repeated the process again with the same results.
The 2nd driver was a K120 that was reconed(reconer unknown), I was assured it was professionally reconed with authentic JBL parts. The drivers were installed in wood horns that a friend of mine borrowed to see if he liked the sound or not. He claimed that he and his wife were listening to the music and it just quit all of a sudden. He too uses tube amps.
I received the drivers back the other day and measured the DCR. One of them was 6.8 ohms and the other 44.6 ohms. I took the battery and tapped the terminals and remeasured the DCR which was 6.7 ohms at this point. I knew at this point it was deja vu all over again!
What companies/countries are suppliers for JBL recone parts anymore???
This really hurts us audiophiles who use vintage JBL drivers. I can't afford to keep reconing drivers due to bad parts.
Just letting off steam!
Regards, Ron