2234 Butyl Surrounds from Japan

[grumpy]

Tried ordering those (-1 version) from the folks in Florida quite awhile ago and got blank stares (not too surprising at the time).
If you eventually make some progress, please let me know

[srm51555]

Funny. I'm looking to upgrade my current mains from 4430 to a modular that includes a bass cabinet with SAM1HFs up top. I have a spare pair of 2235s but truly desire a 2216nd to supply the bottom end. In the interim, I have designed a cabinet that would perch the SAMs up top and be compatible with both 15" drivers. Do you know off-hand how much smaller the cut-out is for the 2216nd?

For the 2216nd the mounting hole diameter is 13.78" and the 2235 is 13.96875" when front mounting. I've been waiting for someone to do the 2216/SAM1HF combination. Keep us updated if you do decide to do this.

Thanks,
Scott

[Ed Zeppeli]

For the 2216nd the mounting hole diameter is 13.78" and the 2235 is 13.96875" when front mounting. I've been waiting for someone to do the 2216/SAM1HF combination. Keep us updated if you do decide to do this.

Thanks,
Scott

Thanks for the info. Seeing as how I'd like to recess the drivers (flush mount) the differing dimensions could make it difficult. That's been my hesitation all along. I may have to hold off until I have the 2216NDs in hand and build them then.

Either way, I'll definitely keep the board posted.

Cheers,

Warren

[4313B]

tried ordering those (-1 version) from the folks in florida quite awhile ago and got blank stares (not too surprising at the time).
If you eventually make some progress, please let me know

320-0045-002 = 2216Nd-1
Note that GT used a 5.0 cu ft (142 l) box tuned to 36 Hz for 4367
Compare to S4700 with 4.78 cu ft (135 l) tuned to 32 Hz for 320-0045-001 = 2216Nd = NLA

[Ed Zeppeli]

320-0045-002 = 2216Nd-1
Note that GT used a 5.0 cu ft (142 l) box tuned to 36 Hz for 4367
Compare to S4700 with 4.78 cu ft (135 l) tuned to 32 Hz for 320-0045-001 = 2216Nd = NLA

Well, that answers a few questions right there.
Thanks

[pos]

320-0045-001 = 2216Nd = NLA

[grumpy]

Note that GT used a 5.0 cu ft (142 l) box tuned to 36 Hz for 4367

thanks! ... P/n suffix kinda has a certain logic to it

[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?

[BMWCCA]

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

With tires, grip and longevity have an inverse relationship. Look at what a great job we did with space-shuttle heat-tile adhesive, or Morton-Thiokol o-ring seals on the boosters.

People who want a better handling vehicle will pay to replace sticky tires more often. Those who don't care, buy bricks warrantied for 90,000 miles. It mostly depends on whether you drive an appliance—or something more engaging.

[JeffW]

Maybe eventually someone will come up with a synthetic foam material that can last forever and at the same time provide the required compliance?

I would imagine all foam materials used on surrounds are synthetic - what natural foams do we have? Sponges?

As for something that can last (nearly) forever with the required compliance, you might take a look at post #1 of this thread

Look at what a great job we did with space-shuttle heat-tile adhesive, or Morton-Thiokol o-ring seals on the boosters.

Actually, the adhesive works pretty well considering what it has to endure - no shuttles were lost due to the adhesive failing. And the o-rings worked fine for all launches where they were used in their specified temperature range.

[1audiohack]

All in a year I have learned that:

Anyone really can be the US president.

Anyone with enough money can buy JBL/Harman.

Butyl rubber surrounds can indeed work even though this experiment caused as much uproar as the above two combined!


I wanted to report that although it is just over a year later that I am absolutely delighted with these surrounds. I don't hear or measure any difference at all between the re-edged set and the re-coned set. With the Fs being within 1Hz of the original I believe these will be what I use going forward.

One point of clarification. On the first page I stated that the roll width was slightly narrower on the butyl replacements than the old JBL originals. This appeared to be the case with the failing 30 year old surrounds but they are identical to the surrounds on the JBL C8R2235 that I built to run while the original 2234's were out for repair.

Still a winner in my book.

All the best,
Barry.

[RMC]

Hi Barry,

I'm glad you bring back this Thread from a year ago I had not seen before. Great idea to test an unconventional solution to a common problem. It gives us one more driver repair option to consider for foam rot. Plus, I'm in the process of re-foaming my 25 yo 2214H drivers, but instinctively purchased new foams specific for this driver, instead of generic foams "one model fits all 12 drivers".

The thought of using Butyl rubber surrounds never even crossed my mind. If it had, and supposing some were available for my drivers (which I don't know), I'm not sure I would have dared to use Butyl surrounds, since I also like my things proper as you say. But your experiment (measurements and listening tests) is quite interesting for me and could make me change my mind in the future as to what is "proper"... Specially considering I like to keep my things working for a long time and having to re-foam is a pain in the neck.

However, there remains in my mind a technical question which may not have been addressed in this Thread and that is the Vas T/S parameter JBL defines as " Volume of air having same acoustic compliance as driver suspension". Could that be modified, maybe extensively or not, by other foams or Butyl rubber surrounds ? Also, will the new suspension behave the same and allow similar cone travel ?

In D.B. Keele's formulas to design a vented-box, the minimum T/S parameters required are Fs (which you measured), Qts (which Ian commented on) and Vas (which may have fallen in between two chairs ?). That Vas used to determine Vb must be important since it belongs to the short list of required numbers.

That's the bugger I'm wondering about regarding new foams or Butyl rubber surrounds, both not being the original stuff. What happens to Vas in the "modified" driver and its impact on cabinet Vb, shouldn't that be considered ? Is it still appropriate ? Box tuning Fb still suitable ? Low frequency response same as before? I wish many members would comment on that issue, as I don't have a definite answer, but my impression is that some things may have changed and/or have to be changed to be optimal.

Your listening tests seem quite positive and that's a very good start, plus we know such a modified driver will still reproduce sound: maybe very well, acceptable or not so well in some cases, since parameters may not be optimal anymore. I have read in many Threads here positive comments from people who have re-foamed with other than original stuff (as is usually the case including mine), but I can't remember seeing one where the "client" isn't satisfied and explains why/what's wrong. That leaves me somewhat puzzled, must be because I assume they can't be all "homeruns" all the time...

BTW I don't recall you mentioning from whom you got the Japan Butyl rubber surrounds, other than mentioning Bay. I would imagine pricing to be much more expensive than equivalent foams ?

Thanks. Best regards,

Richard

[RMC]

Since I have no intention of extending inappropriately, reviving nor stealing this thread, I will soon continue with the interesting info I have found on this matter, in my own Thread called "Hybrid Reconed Drivers..." in the Tech Help section, it also addressed re-foam jobs with other than original stuff.

The reason being, in my view there are still a number of important and outstanding issues for the driver re-foamers and to some extent for the speaker builders. See you soon guys in the "Hybrid" Thread.

BTW I'm surprised at some of the comments Barry received here like "you shouldn't have done that or why did you do this to a JBL driver" type of comments (judgements). Instead, I see this has a valuable and feasible opportunity (i.e. additional option) for the many re-foamers here, like me. I think we should be grateful for benefiting from this experiment for free ! He spent a lot of time installing, measuring and listening, some money too and could have kept his mouth shut while enjoying the music, but he rather decided to share the experiment and his results with us, up to a year later... Anyway, Thanks for all of us Barry.

Richard

[1audiohack]

Hi Richard;

You can hijack away if you want to but a separate hybrid thread will be more fun.

The noise about modding drivers was expected by me to some extent, and I actually think it's funny. This was such a small sin compared to what I have done in the past. There is something mildly disturbing and yet perversely satisfying about say, pushing a hole saw through the roof of a brand new zero mile Porsche.

I don't know how many brand new cars we have cut up to make into racecars at this point. We got pretty good at it, we could completely shell out a brand new car in about five hours and have it on a trailer to be acid dipped. Don't missunderstand, we don't just destroy stuff for fun but in the end, it's just stuff.

I am looking forward to your thread and will try to find some of my own hybrid driver measurments.

All the best!
Barry.