2234 Butyl Surrounds from Japan

[1audiohack]

Hi All!

I have in my office a pair of 4435's that were built in 08-1986. They are original and the surrounds lasted just a few months shy of 30 years. One of them just started to crack, yeah I know, terrible design, only 29.5 years of trouble free service.

I have never re-foamed a speaker, I have always just re-coned them but I had seen on the bay these butyl surrounds from Japan and I figured if anyone was going to get this right it would be them. What the hell? What have I to loose? If they don't behave I will just re-cone them anyway so I bought four.

The first thing I learned is that if you value your time, just re-cone!

I haven't taken pictures yet but the roll is slightly smaller than the JBL surround. It fits the cone perfectly but leaves a slightly wider flat between the outer edge of the roll and the front foam gasket. This may not be noticeable to the average person but most of us would see it.

Other than that? Pretty close to perfection.



The graph curser numbers didn't display so here is the rundown:

17 Hz Fs is with the original surround removed, no surround at all.

21.6 Hz Fs is with the original failing surround.

24.0 Hz Fs is with the new butyl surround installed.

Because I didn't want to be without music at all I re-coned four 2235's to 2234's while I went through this experiment. I swept all four of them of course and the average Fs of four of them is 24.4 Hz.

I will get these back in their original homes tomorrow during lunch and see if I can hear any difference from the new ones going back to these.

All the best,
Barry.

[4313B]

Interesting!

They are original and the surrounds lasted just a few months shy of 30 years. One of them just started to crack, yeah I know, terrible design, only 29.5 years of trouble free service.

Maybe it is a desert thing... I've noticed that the environment has a large effect on when exactly the foam surrounds fail. I think it is quite interesting how we forgo alleged superior performance for functionality. Greg mentioned a couple years ago how fantastic lans-a-loy was from a performance perspective but it had no longevity, hence the foam surrounds of the 2231/2234/2235, etc.

As an aside, years ago I purchased a whole bunch of recone kits from JBL that all contained foam surrounds in a very advanced state of rot. I should have kept the photos. In any case, JBL ended up crediting me for the kits and they all ended up with Rick Cobb refoams. A few months later when I went to order a few more of these kits I was told that the remainder had been destroyed. I could have simply refoamed them.

[Flodstroem]

I was told that the remainder had been destroyed.

Oh my god

[hsosdrum]

Interesting!

I've noticed that the environment has a large effect on when exactly the foam surrounds fail.

That's for sure. Here in smoggy L.A. they have a considerably shorter lifespan than in areas that are comparatively smog-free. The same is true for the rubber drive belts on turntables and cassette decks (remember those?). Butyl rubber surrounds seem to be relatively impervious, thankfully—I've had my rubber-surrounded HT speakers for 20 years with no apparent degradation.

[Joseph Smith Jr]

I have never re-foamed a speaker, I have always just re-coned them but I had seen on the bay these butyl surrounds from Japan and I figured if anyone was going to get this right it would be them. What the hell? What have I to loose? If they don't behave I will just re-cone them anyway so I bought four.

The first thing I learned is that if you value your time, just re-cone!Barry.

I cannot imagine why on earth you would do such a thing to such beautiful drivers, makes not one iota of sense to me when the closest to the original you're going to get is readily avaluable and is of a known quantity as well as being supplied from a well established and known to be excellent vendor
Especially as you claim that you value your time

And who knows, with a quad of Rick's surrounds those bad boys might just meet or exceed specs, you never know, but regardless, definitely a heck of a lot less of a gamble involved and at least they'd look correct

Bizarre

Hope it all works out

[JeffW]

I cannot imagine why on earth you would do such a thing to such beautiful drivers, makes not one iota of sense to me when the closest to the original you're going to get is readily avaluable and is of a known quantity as well as being supplied from a well established and known to be excellent vendor
Especially as you claim that you value your time

And who knows, with a quad of Rick's surrounds those bad boys might just meet or exceed specs, you never know, but regardless, definitely a heck of a lot less of a gamble involved and at least they'd look correct

Bizarre

Hope it all works out

Man, they are just 2234s, not some rare and irreplaceable masterpieces. Recone kits are still available. You make it sound like he painted a butyl moustache on the Mona Lisa. JBL is moving away from foam surrounds in favor of rubber, I'm not sure any of their new production designs still use foam. He clearly stated it was an experiment, and he certainly has the skill and resources to perform an inexpensive experiment on some extremely common drivers.

Good example of that is what he sells to replace Lans-a-loy surround, they exceed even the parameters as defined when the drivers and the Lans-a-loy were new! And the fit of every surround I have ever bought from him, quite a few, is second to none, ID", OD", roll width and compliance

Wait - now you are advocating replacing surrounds with something other than what JBL used?

[Ian Mackenzie]

Storm in a tea cup!

I have to say when a foam surround starts to go it's very annoying.

I am in favour of challenging the convention.

[Ian Mackenzie]

What interesting is the 2235h found its way (and the 2235 recone ) into many 2231 based boxes and no one gave a rats about the specs (16 Hz versus 20 Hz)just bolt it in and let it go. Ie the 4343.

But most people agreed the 2235 sounded a bit different.

[4313B]

Strangely I ended up with J.M's cloth surrounds on all my LF transducers (2216Nd and 1501AL-2). Full circle. Cloth - Lans-a-Loy - Foam - Rubber - Cloth - The End.

[1audiohack]

Hi Thomas!

I have not re-measured them yet.

It's hard to be mean to them, they get loud so fast so easily. I am currently driving them with one of the M2 project amps (I-TECH 5000 HD) and I can't even get the -20dB LED to ever even flicker before I am ready to run.

You are probably right, I should just leave them alone. I might be able to talk myself into it.

Hi Bart!

If I cut them out I will definitely try to save them for you.

All the best!

Barry.

[Doctor_Electron]

Storm in a tea cup!

I have to say when a foam surround starts to go it's very annoying.

I am in favour of challenging the convention.

+1

Dealing with rotten foam surrounds sucks. I'm sure a company with the resources and technical excellence of JBL at the time when foam surrounds were implemented could have come up with a more excellent design.

I am more interested in longetivity than originality considering how many expensive JBL systems I've had to spend money on to repair after their rot-out. And re-foamed drivers are original? Not exactly.

The "convention" sucks.

[Joseph Smith Jr]

+1

Dealing with rotten foam surrounds sucks. I'm sure a company with the resources and technical excellence of JBL at the time when foam surrounds were implemented could have come up with a more excellent design.

I am more interested in longetivity than originality considering how many expensive JBL systems I've had to spend money on to repair after their rot-out. And re-foamed drivers are original? Not exactly.

The "convention" sucks.

No more than having to replace worn out tires on a Rolls-Royce
Just part of the experience of owning machines that move and do stuff, parts of it are going to wear out or change eventually
Don't think anyone can stop that
You'd think that with all of the resources and technical excellence of the space program someone could make tires that never need replacing and that work just as well as the ones that do
I have tried off and on over the years to narrow things down to owning only systems that used either pleated paper or cloth surrounds
Ain't gonna, just never seems, to be able to happen
Even those change performance or degrade over time, just might not be able to see it
Maybe eventually someone will come up with a synthetic foam material that can last forever and at the same time provide the required compliance?

[Joseph Smith Jr]

Wait - now you are advocating replacing surrounds with something other than what JBL used?

Lans-a-loy was eventually classified as a factory defect by JBL and treated as such and ultimately abandoned altogether, so in this instance, yes

And I wasn't making a big deal out of it, only that it would only yield truly meaningful results if compared, side by side, to two drivers with new surrounds of both types, not one on it's way out versus the new rubber one

I have had more than a few re-edge jobs meet factory specs completely, so in my view why screw with a good thing? Especially after the OP also made it clear that he usually re-cones anyway as a matter of personal practice

Those rubber surrounds have been around for a long time, Part Express has been hawking them for years, or at least they were

All I am saying is that if I a going to spend the time, and time is something once spent it is gone, to patch a driver, I'm at least going to try and use the closest thing to an original or correct part, known quantity, as is possible

Might consider the switch for some really nice high quality or specialty fit automotive driver, but otherwise I don't see the point as an end user, manufacturer? Yeah

Either way though, I wasn't making that big a deal of it, just wouldn't do it myself unless someone like Greg Timbers gave me a specific part number and said "here, use these instead"

[Joseph Smith Jr]

He clearly stated it was an experiment,

I got that part of it too

[1audiohack]

Hi Joseph;

This was an experiment, nothing more. I wasn't looking to save money or time, simply to try a surround made from a material that is widely used by JBL and many others. Normally I wouldn't even bother to re-foam these, I would do the most correct thing and buy new JBL C8R2235 cone kits and keep them all 100% JBL.

Meet or exceed factory specs? Being within a couple of Hertz Fs is plenty close to me.

The truth is that these 30 year old speakers as great as the are/were, have been absolutely eclipsed by the new large format JBL monitors. That's why they ended up in the office.

I have thought about gutting the crossovers, replacing the woofers with 2216's and making throats for the 2344's that would use an 1.5" throat driver like a 2451 or D2430K but your still left with a 35 year old horn and that would be a waste of an otherwise near pristine pair of 4435's.

It is likely that I will soon re-cone these anyway because I like things proper. If the re-cones last like these did I will be 84 when they get weak again and I doubt I will care much by then.

So here is the intended value in this experiment, there is for those who hate the foam thing, a butyl surround that performance matches the 2234/2235 stock surrounds. Cobbs not the only game on the planet. There is a good non foam option, not for purists maybe but these guys have butyl surrounds for many others as well.

All the best,
Barry.