New foam on L26, L15 L100 and L112

[Sound_sensible]

I have just some questions on refoaming some jbl speakers. I know L15 and L26 have a foam suspension and sometime they need to be refoaming. How often to they need to be? are new foams kits more resisting and last longer? i also would like to know, on the l100 and l112 speakers there is not a foam on the woofer, but a cunt of tissue. Does this material need to be change as foam suspensions? or does it is a life suspension?
Thank you in advance
Regards

[grumpy]

when they go bad (cracks, missing pieces, obvious deterioration, ...), not predictable.
yes.
This is not true of the L112, which does have a foam surround on the 128H driver, but:
no.
yes.

[Sound_sensible]

Thank you grumpy. Sow only the l100 has the no foam problem. Are they are other jbl speakers than dont have this problem? thank you
regards

[grumpy]

I would turn that around and say the L100 does -not- have the foam deterioration problem,
as it has the cloth/accordion surround. Perhaps this is what was intended in your reply?

However, even a cloth-surround speaker often has a gummy substance applied to the surround,
(providing a air-seal and some dampening) which can slowly migrate or pool at the bottom of the
surround ... causing some people to remove the affected speaker, rotate it 180º, and then
remount it ... to allow the "goo" to re-flow with gravity (perhaps once per year or less often?).

Other drivers have -paper- surrounds, sometimes similarly treated, that can also deteriorate
with use and age.

I do not have a list of what JBL speakers used foam vs. paper or cloth surrounds.

[rdgrimes]

L15: butyl surround that cracks and needs replacement. Even if it doesn't crack right away it does get pretty hard and rigid. At this point in time they should be replaced just on principal.

L112: foam surround.

[Sound_sensible]

grumpy yes thats what i would like to know. Its true i had a pair of L15 and the foam was geting pretty hard. Sow i trade them with a friend for a L26 pair with new foams. And now someone propose me a nice paire of L100 century. The sound is better, i already love the sound of my l26. Sow the only thing will make me change it the fact i dont need to change the foams. But their problem is that the paper cone was re paint with white paint. I dont realy like tis kind of mod. The l112 is a guy near me selling a pair, son thats why i ask if they wear the same non foam suspensions as the L100. i dont realy know what to do :S Life can be so hard :)
Thank you guys :)

[Sound_sensible]

rdgrimes i'm pretty sure on the L15 is also foam suspensions, like on the l26. Is on the 18ti the butyl suspensions.

[rdgrimes]

rdgrimes i'm pretty sure on the L15 is also foam suspensions, like on the l26. Is on the 18ti the butyl suspensions.
Incorrect, the L15 uses the 115H woofer which came with the butyl surround. As did the L46 (117H) and L56 (118H). I have re-foamed all 3 of those.

[Sound_sensible]

rdgrimes butyl is like rubber no? i saw a pair of 115H-1 the have rubber suspensions, but on the L115 is more like the suspensions of the l26 i have.
The true is that i m not sow sure what butyl is :blink:

[brutal]

Incorrect, the L15 uses the 115H woofer which came with the butyl surround. As did the L46 (117H) and L56 (118H). I have re-foamed all 3 of those.

I'm looking at an L15 sitting on my desk right now and they appear to be foam. The L56 in the other room are also foam as far as I can tell. I think there's a misconception they're butyl rubber because the composition is denser than the more compliant larger sized foam surround drivers. If they're butyl, they're not shiney and JBL engineered "pores" in them that look like and feel like foam.

Is it possible JBL had later runs or replacement drivers that may have had butyl surrounds?

Sound_sensible - 115H-1 has a poly cone, (shiny) butyl surround and black flange face. Found in 18Ti and L20T series.