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Classic JBLs with Aquaplas surrounds...

This probably belongs on a vintage hobbyist site on on the tech forum, but I figure that many of you, as I, have a pair or two of early '70's JBLs around. I have a quartet of S109 Aquarius IVs, which use the special LE-8T2 full-range driver. The only important part of this is that these drivers do not use foam or butyl rubber for their surrounds, they use a material known as "Aquaplas," wich is buff-white and generally becomes more rigid over the decades as it dries out. This ultimately can destroy the cone as it increasingly limits their travel. I disassembled one pair and found one crack in each surround of otherwise mint drivers, so sent these off to an experienced specialist for modern foam surrounds. They decided that the Aquaplas was too difficult to remove from the cones, so did a total recone at a big discount as they had not originally thought it was necessary.

Drivers are now well rebuilt, but totally non-original. The second set of drivers have pliant and uncracked original surrounds (this pair probably experienced better climate control prior to my buying them). I keep thinking that I should have maintenance done on these as well, as they are approaching 40 years in age and I intend to keep them indefinitely-- I run them in quad with the other pair and I'd like to keep their performance parameters the same-- I've also had the vintage equipment driving them rebuilt.

I want to double-check before I permanently alter my pristine pair: Do any of you own JBLs with this type of surround, does Aquaplas ALWAYS deteriorate in a living-room environment, and has anybody removed Aquaplas without damaging their cones? Were these guys experienced, but just lazy?
morgenholz
xiekitchen
819 posts
 
Aquaplas was a cone treatment material to add dampning and mass to a woofer cone. It is not a surround material. It was sometimes added to the front of the cone, as in the woofers on the JBL L-100, or on the rear, such as on the L-66's woofers and later versions. You should be able to replace a surround, Aquaplas-coated cones or not. BUT it is usually recommended to perform the re-cone on 70's era JBL woofers regardless... JBL makes OR at least made, unless they are no longer doing it, exact cone replacements for all woofers. It's just not cheap to re-cone.
regards
morgenholz OP
61 posts
 
Thanks all, yes, I tend to trust the tech who did these, and intend to use the two pairs as a quartet, and love them, so I should probably stay on-plan.

Xiekitchen, thanks for the clarification-- I had been advised by a third party as to what "Aquaplas" is, and apparently he was off. The LE-8T2 uses an untreated cone, unlike the LE-8T, and the surround material bonds very tightly to this.
xiekitchen
819 posts
 
Morgenholz: ok I think I see what your problem is.. the surround material cannot be removed very well without messing up or damaging the cone.. then yes it is better to just recone them.. AND JBL should be able to provide exact correct replacement cones and voice coils for those drivers ..? unless they cannot do this anymore? I had a pair of 12" woofers redone about 8 yrs. ago (by a local JBL authorized service center), no problems, they sound great.. just took a while for the new woofers to sort of 'burn in' and then they opened up with that JBL bass.
morgenholz OP
61 posts
 
Xie, correct regarding surround material-- I also bought a pair of L166 had had the 12" surrounds replaced with OEM.

However, the white surrounds and black, untreated paper cones are no longer available, but are now replaced with equivalents including voice coils. I'm gathering that this is better than another forty years with original parts...
jr_w
27 posts
 
The surround material you are referring to is called Lansaloy. Once you know this, then a web search will yield a variety of threads on refurbishing them, like This One
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