Ring Radiator Production

[blackwell]

Thought you might get a kick out of this, hopefully it's new info for you.
One of the guys I work with (he shall remain nameless) working at JBL Pro for over 20 years and over the years went from the line to engineering. Anyway, he told me about the production of the ring radiators 2405 etc. The production yield was very low. Fall out because of the high standards for frequency response JBL required was killing them. Then a lady on the line figured out a way of fixing the diaphragms that did not pass. The tooling guys tried and tried to implement this fix into the die but they just couldn't get it to work as well as her method, she had the magic touch. And what was this method? She would simple run the tip of a ball point pen around the diaphragm, this added crease made the diaphragms play very smoothly and within spec. I don't know if this is true but he swears it is and says that you can see it on many of the old diaphragms if you look closely. It's a great story, especially how the tool guys couldn't duplicate the results, a personal touch.

[Steve Schell]

Hi blackwell,

Welcome to the forums.

I heard this same story from ex JBL Vice President Garry Margolis and have told it a time or two here.

It makes sense though, as the cross section of the diaphragm is a shallow V. There is really no way for it to move without distorting the diaphragm surface in some way that would most likely be harmful to the response. Adding a tiny bit of compliance at the edges would allow it to have some excursion without oilcanning the surfaces.

[scott fitlin]

I have heard that story, dont know if its really true, but since Steve says he heard it from Gary Margolis, it might be.

One thing I do know though, is that in the last several years, sales of tweeters had declined. Really the only ones that were seriously using tweeters much anymore were dance club systems, all the pro and touring rigs have CD horns that go all the way up.

If the story about them not being able to get the diaphragms to spec because of a pen poke in the right spot is true thats really kind of sad! How could a company like JBL not know how to make their product work?

[Harvey Gerst]

I certainly don't recall it ever being done during the production of the original 075.

[Ian Mackenzie]

It explains a lot. I have not seen two 2405 responses the same yet!

[scott fitlin]

I certainly don't recall it ever being done during the production of the original 075.Hey Harvey, there have been so many stories over the years.

One story I have heard many times, is that the aluminum they used to use years ago was different and better quality then the aluminum used in the last 10 to 15 years. Is there really any truth to this?

One story someone once told, is that JBL used to go to the WWII aircraft graveyard and buy scrap aluminum off the war planes and that it was better than the later aluminum.

Its another tale that has been told!

What say you?

[blackwell]

I have heard that in the "old" days JBL used a softer alloy. Then in an attempt to enhance the life span of diaphragms and increase high freq. resp. they went to a harder alloy. The older diaphragms would work harden and break like glass. But of course, I've seen AL diaphragms made in the early 80's just before Ti that broke like glass too. Who knows?

Eric

[Harvey Gerst]

Hey Harvey, there have been so many stories over the years.

One story I have heard many times, is that the aluminum they used to use years ago was different and better quality then the aluminum used in the last 10 to 15 years. Is there really any truth to this?

Possibly true; I don't know what they used in the last 10 to 15 years.

One story someone once told, is that JBL used to go to the WWII aircraft graveyard and buy scrap aluminum off the war planes and that it was better than the later aluminum.

Its another tale that has been told!

What say you?
Scrap aluminum from WWII aircraft graveyards? LOL!!! I don't think so.

[Baron030]

Gee, who needs Adam Savage or Jamie Hyneman, when we have Harvey?
This tread is starting to read like an episode of Mythbusters.

Harvey can you please tell us some more wonderful JBL myths.
Besides, the top secret military "Brown Note" research at JBL for example?:rotfl:

We all enjoy reading your posts.
Baron030

[scott fitlin]

Scrap aluminum from WWII aircraft graveyards? LOL!!! I don't think so.Well, its one of the stories that float around! I never put to much creedence in them.

What Blackwell posted about the older phragms having a different composition of alloy, that makes sense.

I know that as we got into the 90,s and the big new extremely powerful amps began coming out, power handling became a serious problem. Guys wanted to use the BIG Crown 5000,s and Crest 9001,s, and then power to HF devices began to creep upwards too. As one manufacturer explained it to me, the days of powering compression drivers with 30 watts at a big show are over, and with the older, lighter diaphragms, 75 watts and better, and they were just shattering everything. They had to make diaphragms more withstanding.

This is one of my big problems with vintage gear, and speakers. Unless you have components with the actual 1979 cones and diaphragms, they arent really vintage. If they have been rebuilt with new parts, many times the new parts do work to a degree, but are NOT 100% like the parts originally made and used.

[Harvey Gerst]

Gee, who needs Adam Savage or Jamie Hyneman, when we have Harvey?
This tread is starting to read like an episode of Mythbusters.

Harvey can you please tell us some more wonderful JBL myths.
Besides, the top secret military "Brown Note" research at JBL for example?:rotfl:

We all enjoy reading your posts.
Baron030
I don't remember any "brown note" research, but Ed May came damn close to it when we were on Casitas. Ed built a very long throw, low distortion LE15, and mounted it in a large cabinet located in the corner of the sound room, and fed a 27 Hz sine wave into it at a pretty high volume. No overtones, just pure 27 Hz.

When you walked into the room, it felt like you were underwater; you could barely breath, let alone talk. Most people couldn't last more than a few seconds in the room without coming out sick.

I still remember that experience to this day.

[Harvey Gerst]

Well, its one of the stories that float around! I never put to much credence in them.

What Blackwell posted about the older diaphragms having a different composition of alloy, that makes sense.
On further reflection, there might be some possible truth to that story, but not the scrap metal part of the story. You must remember that Bill Thomas worked at Marquart Aircraft for a number of years before JBL, and Bill was still very close to Roy Marquart.

It is possible that he worked out a deal with Marquart to buy higher grade aluminum from them at a lower price, because of Marquart 's better purchasing power.

Johnny Edwards would know more about that than I would. Anyway, all this is pure speculation on my part.

[scott fitlin]

Interesting!

Harvey, your the best.

:)

[Harvey Gerst]

Interesting!

Harvey, you're the best.

:)
Nah, I'd say I was "blessed", not "best". I was just very lucky to be in a lot of right places at exactly the right times.

[scott fitlin]

Nah, I'd say I was "blessed", not "best". I was just very lucky to be in a lot of right places at exactly the right times.Well, however you want to put, you put a good ending to a story thats been floating around for a while.

And this ending actually makes sense, if a manufacturer can get something cheaper, and at the same time, better, YES, it could very well be.

Aircraft grade materials are known to be some of the best available.

:)

[hardtime]

Speaking of tweeters, I have a 2405 and some one has pushed one of the locator pins down flush. What is the fix for this?
Thank you

[SMKSoundPro]

Speaking of tweeters...


I have had VERY good luck with 2402,2404,2405 magnet assemblies(motors) that have been dropped and the top plate glue joint has let go, sending the outer ring towards the pole piece with outstanding magnetic force!

My friend, the Admiral, machined a centering jig for me with two brass locator insert pins, so that the top plate can be re-glued and centered, perfectly! It is SO simple. I have reglued four motors, so far, and all of them have come out great!

Remember my wife's motto: "No more JBL paper weights!"

I will send photos to show, soon. I did not have my camera at work that night, but can assure you that end product will be a useable tweeter motor! (I do not have a gauss meter, and can make no assurances that some flux density is not lost in the process.) But they do sound exactly as loud as an alnico or ferrite motor tweeter when A-B'ed.

If any of you have these "paper weight" tweeter motors where the top plate has shifted, please consider sending them to me, and I will re-glue and re-center them and mail them back to you.

Always trying to help when asked,

Scott.

PS> If you have a 2410, 2420, 2440, 2470 0r 2480 style of driver with a problem, please contact me also, as the Admiral and I came up with a jig to fix a problem I had with a 2470 to become a 2420.

[blackwell]

Here's another 2405 story I was told.
When 2405 production was stopped due to running out of metal phase plugs they used to just grab 077 plastic phase plugs and spray paint them black. I know it sounds sloppy but the thickness of paint is so thin that I don't think it would hurt and after all they did pass QC. It's just interesting to think that someone out there has a nice prism painted black:)

[blackwell]

Hi blackwell,

Welcome to the forums.

I heard this same story from ex JBL Vice President Garry Margolis and have told it a time or two here.

It makes sense though, as the cross section of the diaphragm is a shallow V. There is really no way for it to move without distorting the diaphragm surface in some way that would most likely be harmful to the response. Adding a tiny bit of compliance at the edges would allow it to have some excursion without oilcanning the surfaces.

I have just confirmed this story.
I opened up a 077 and pulled out the diaphragm. It was an original blue JBL diaphragm and under a microscope you can clearly see the pen mark. It goes all the way around the diaphragm outer edge where the V meets the outer blue ring. The slight groove left behind even has ink on it from the pen. Very cool. Thought you'd like to know.

[Hofmannhp]

Hey Harvey, there have been so many stories over the years.
....One story someone once told, is that JBL used to go to the WWII aircraft graveyard and buy scrap aluminum off the war planes and that it was better than the later aluminum.
.......

Hi all,

this myth can be busted......

airplanes are made from Duraluminium (short: Dural) and this material, with values like steel, can not be formed like you need to form it for a dia.
Dural is 95% aluminium, 4% copper and 1% magnesium and very brittle.

HP

[scott fitlin]

Hi all,

this myth can be busted......

airplanes are made from Duraluminium (short: Dural) and this material, with values like steel, can not be formed like you need to form it for a dia.
Dural is 95% aluminium, 4% copper and 1% magnesium and very brittle.

HPJBL has always said they make their aluminum diaphragms from Duraluminum!

What I have learned thru the years, is that the older phragms were lighter and thinner. However, when we got into the 90,s, and the power amps got more powerful, and they were shoving 75w into drivers designed for 30w, etc, they kept shattering the phragms.

The manufacturers made a heavier, thicker phragm, that could handle the workload, but, the sonics changed.

I had a long talk with one MAJOR manufacturer, who I wont name, and I alsked why cant you make both? Heavy Duty, and light weight, let the user choose what they need? The manufacturers response was its too costly to have two parts for the same driver, and the tour sound companies will never go back to what was, and if they make the older style phragms, they will just keep blowing them with high power. He also told me that reputation of consistency and reliability is an important factor for any company, so they make what works for the current trends in audio.

Now, my own personal opinion, companies are in buisiness to sell products and make money. Just as I am too. They cant make money selling parts for old, discontinued items. They need to sell NEW products, too.

It is what it is!