Question: What is the difference between old, almost gone foam surrounds and new foam

[transducergeek]

Has anyone tested, or experienced and heard the difference between super compliant old nearly falling apart but still intact foam-surrounds, which might allow greater excursions of cone, and brand newly installed foams which are fresh and relatively stiff units when compared to the say, the condition of 12-15 year old types found originally on used speakers. Fs might be different? By how much?? Will I hear less deep bass with fresh foams?? What is the best method to "break-in" new foams? A certain frequency? General music? Thanks for any information on this subject.. T.G.

[macaroonie]

4 HOURS OF MOTORHEAD SHOULD DO THE TRICK

[Chas]

If you search this site, I think you'll find that the folks who know JBL, say that it really doesn't make any difference. In fact, I think Giskard ran some tests before and after of Fs and came to the same conclusion.

My understanding is that it is mainly the spider that dictates compliance, not so much the surround.

[Thom]

I havn't got new surrounds on yet but the difference between the old somewhat pliant not very dammaged looking surrounds. And the same surrounds treated with brake fluid that aren't stiff at all and show every imperfection that they have picked up over the years and look as though they will probably last until tomorrow but you cant be sure is night and day. So unless the new surrounds have as little body as these currently do the surrounds do provide a fair amount of the support. In the case of the 135A which has a very heavy cone I believe the cone actually sits in a different place with the magnet up than with it up. I don't use it in either position so this doesn't seam to be a problem but once the surround adds nothing to the suspension you can tell that it did. Sound wise I haven't worked with them under conditions that would alow me to fairly judge, I do have an opinion.

[Zilch]

Measure the Fs before and after, and compare to spec for the driver.

Surrounds do come in various materials, thicknesses, and resiliancies. What's the correct aftermarket surround for any particular driver seems to be a trade secret. (Read "crapshoot" here.)

The proof is in the result - I can't get 116A/H refoam Fs under 30 Hz, while GordonW does, routinely.

[I'm trying a factory recone kit next.... ]

[Rolf]

As said many times: re-cone, no re-foam. The only way to be sure. Why do you think JBL do not offer foam only?

[transducergeek]

What I mean is, if you have a K2 or other High-End JBL system, (L300's?, 4350's, S8R??) Then, sure spend a few hundred on the woofers, it's a small percentage of the total value... But if you are trying to restore a pair of L100T's that you buy "rotted" for around $200.00, or something else like it, to re-sell, worth really about $300.00 or so, when perfectly restored in the used market, it's not fiscally practical to put hundreds into just the woofers, you will lose money on the final transaction... Re-foam is the only reasonable (about $10.00/pair in parts, instead of spending about $300.00/pair in obtaining new 2214H-1 cone kits) way to repair a "medium-end" JBL system found with bad surrounds of foam, to operational function, sounding good, ready to re-sell, and make a little Wampum for your time/trouble.

Anyway, what I was really asking in my original post, was... Are really old, foam surrounds more flexible than brand new ones? How does this sound different, if any difference there is... ? Even if JBL did the original cone, what are the differences in performance with brand new, vs. really old, but not yet torn foam surrounds???? Do 12 year old JBL's with foam surrounds sound different than when one year old???? IS there more low end? Or not? Thanks, Rolf... (The other Rolf)

[grumpy]

Hey Rolf. Having recently purchased a set of otherwise very nice L100T's that had
rotted foam surrounds, I can tell you that there is no way I would play them loud enough
to make a significant audible difference prior to replacing the foam. One was missing
pieces of the surround, the other was "complete" but ready to disinegrate on contact.

I did replace the worse surround first and listened to both systems prior to replacing the
second surround, but unfortunately can not tell you anything conclusive. I'm not sure
I understand you're concern other than the question of how one knows they have the
"right" surround prior to installing it... and I don't have the answer for that either.

If I remember, and have another refoam "opportunity" I'll try to do a WT2
before/after comparison.

-grumpy

[remusr]

The performance of old surrounds could vary in any direction depending if they are stiffer & tending towards cracking (due to a dry atmosphere or being Lansalloy), or rotting apart due to humidity and pollution, the more common problem.
But I think your question might be how do aftermarket refoam kits stack up to original sound? My aftermarket foams and conekits have ALL been stiffer than JBL conekits or new drivers with Fs for 2235's being typically in the 24-27Hz range and for 2245's in the 30Hz range vs original 20Hz for both. JBL cone kits were usually 0.5 to 2Hz high when new but that has lessened a small amount, 0.25-1Hz, with some use for a couple I re-measured.
Soundwise I would say the aftermarket refoams were somewhat bassier/boomier and less articulate. This may be consistent with their nonoptimal higher Fs in the same cabinet.
A big(ger) issue is the spider - my aftermarket spiders were all stiffer than original or JBL kits and some of my aged spiders were very stiff as well. I do not know why some spiders stiffened with age as I would have thought they would have sacked and been softer. Pollution?
I hope my experience is of some use in your situation.

[Thom]

I don't know this for absolute fact but I'm thinking that if all that is wrong with a driver is that time has taken (time in years not time in hours played) it's toll on the foam surround then a new foam surround with the right foam (I'll leave it to someone else to define right) should be as good as a recone. If the surround is worn out then it makes sense that the spider would also be worn and the VC could be damaged and JBL probably doesn't want to be in the business of making those calls. Just my guess. Another possability is that they are going for max profit but I'm willing to give them the bennefit of the doubt.
Most likely a customer having payed for a refoam is going to expect his speakers to sound new and is not going to expect to pay more. Doing your own and knowing your odds is totally different. I've been in a couple of businesses and one thing I've learned is the customer only wants to pay once. That is more important than how much they pay. So from a business point of view reconing makes sense. That doesn't automaticly mean that to sound right you have to recone.