K140 having foam problem?

[Krischu]

I recently sold two K140/16 Ohms in an original JBL cabinet to a friend. I played the speakers from an amp and heard no noise or scraping or rattling.

Now he says that speaker had developed a problem that had been common to some series. Some air filter foam or whatsoever began to get brittle over time and could only be repaired by removing the aluminum dome and try to exhaust the foam crump through the air hole in the magnet, if one was lucky.

Could anyone comment on this?

--
Christoph

[Earl K]

Christoph,

( For an accurate answer ) a professional reconer really needs to answer your question .

Yes, the internal foam-filter ( common to the ferrite model magnets ) degrades over time and errant particles can gum up the voice-coil's movement in the gap.

but ( IME )>

I don't think any alnico magnet-type woofers were ever originally fitted with the "internal foam filter" ( all the OEM alnicos I've owned, had a hard plastic filter, that aren't known for degrading ) .

mind you >

If those K140's were ever reconed ( it is a 30-40 year old speaker ) they might have been retro-fitted with an internal foam filter ( I see one on eBay right now ) .

typically >

One can determine the type of internal filter by simply shining a focus-able flashlight into the back magnet vent ( though the foilcal on that old series can impede a good look ).