Interchangability of 1,75" diaphragms Altec/JBL

[reVintage]

Googled for new dias for my 808´s. Noticed the same replacements where sold for Altec and for example LE175 and 2425.

As I have never heard of this before I doubt it will work. Or will it? If so it would be interesting to try some of the later JBL in the Altec.

[Earl K]

Googled for new dias for my 808´s. Noticed the same replacements where sold for Altec and for example LE175 and 2425.

As I have never heard of this before I doubt it will work. Or will it? If so it would be interesting to try some of the later JBL in the Altec.

IME, yes the diaphragms are somewhat interchangeable within the gaps / but JBL & Altec use different mounting holes ( in relation to the location pins ). Therefore, you would be forced to drill out some new holes .

Are you talking about buying real JBL & Altec diaphragms or buying counterfeits ?

GPAs price on replacement diaphragms makes it a no-brainer for those on this continent to use OEM diaphragms .

<> cheers

[tomee]

IME, yes the diaphragms are somewhat interchangeable within the gaps / but JBL & Altec use different mounting holes ( in relation to the location pins ). Therefore, you would be forced to drill out some new holes .

Are you talking about buying real JBL & Altec diaphragms or buying counterfeits ?

GPAs price on replacement diaphragms makes it a no-brainer for those on this continent to use OEM diaphragms .

<> cheers

If an Altec diaphragm can fit into a JBL 2410 I'd be willing to give it a try. If it's just a few mounting holes I wonder if GPA would consider selling JBL-compatible diaphragms (although that would be servicing the competition, and he's probably better off selling a new 902 than getting your old 2420s back in service....)

GPA is selling NEW 902-8As on eBay for $202 +shipping. Not sure what replacement diaphragms sell for but that sure seems like a nice price for a complete driver.

[Steve Schell]

Just a little background... Jim Lansing designed the user replaceable diaphragm assemblies for the Altec Lansing large and small format drivers in 1944, as the drivers were being converted from field coil to permanent magnet operation and the top plates would no longer be removable for diaphragm assembly swaps. The driver families were also converted from half roll to tangential compliances at this time. Jim developed a method for hydraulically forming these new diaphragm shapes, which could no longer be formed with a spinning process as had been the case with the earlier diaphragms.

In the first picture below, you can see some radial puckering around the edge of the dome. This is an early Altec 288 diaphragm pressing, found in Jim's workshop in San Marcos by his family after his death. As can be seen he was not quite there with the process, though he worked it out as the production 288 diaphragms looked perfect right from the start.

Jim left Altec in August 1946 and soon developed his own small format driver, the Lansing Sound 175. The second picture shows a pressing of a 175 diaphragm. Note that the tangent at the bottom of the picture, slightly to the right, has a flaw, a little raised bump. This bump can be seen on all (I think) original 175 diaphragms until some time in the mid 1950s, so they were evidently produced until that point using Jim's original tooling.

One more thing... one difference between the Altec and the JBL diaphragms is that the tangents spin in opposite directions. Jim may have done this to differentiate his product from that of Altec.

[scott fitlin]

AMAZING INFORMATION, Steve! Where do YOU find all this stuff?



:D

[Progneta]

Just a little background... Jim Lansing designed the user replaceable diaphragm assemblies for the Altec Lansing large and small format drivers in 1944, as the drivers were being converted from field coil to permanent magnet operation and the top plates would no longer be removable for diaphragm assembly swaps. The driver families were also converted from half roll to tangential compliances at this time. Jim developed a method for hydraulically forming these new diaphragm shapes, which could no longer be formed with a spinning process as had been the case with the earlier diaphragms.

In the first picture below, you can see some radial puckering around the edge of the dome. This is an early Altec 288 diaphragm pressing, found in Jim's workshop in San Marcos by his family after his death. As can be seen he was not quite there with the process, though he worked it out as the production 288 diaphragms looked perfect right from the start.

Jim left Altec in August 1946 and soon developed his own small format driver, the Lansing Sound 175. The second picture shows a pressing of a 175 diaphragm. Note that the tangent at the bottom of the picture, slightly to the right, has a flaw, a little raised bump. This bump can be seen on all (I think) original 175 diaphragms until some time in the mid 1950s, so they were evidently produced until that point using Jim's original tooling.

One more thing... one difference between the Altec and the JBL diaphragms is that the tangents spin in opposite directions. Jim may have done this to differentiate his product from that of Altec.

Those pictures are the most beautiful things I have seen all day!

[Mike Caldwell]

AMAZING INFORMATION, Steve! Where do YOU find all this stuff?




:D



Agreed!!!! Things like that I'll never forget. :bouncy:

[scott fitlin]

Agreed!!!! Things like that I'll never forget. :bouncy:For real, Mike! Forget that Steve has pics of Jim Lansings original work and prototyping. He has the really tiny details of everything, too. To narrow something of this age, down to that JBL probably used Jims original tooling due to a little nib on one of the tangents, talk about a needle in the haystack!

And, I never even knew the tangents for the JBL spun in the opposite direction of the ALTECS!

Steve Schell, YOU are ONE INCREDIBLE INDIVIDUAL, and certainly one of the best LIVING ENCYCLOPEDIAS OF AUDIO I KNOW OF!


:applaud:

[reVintage]

Thanks,

Great info!


different mounting holes ( in relation to the location pins ).

So if I understand this right, the location(centering) pins are in the right place? In that case it should be a walk in the park(almost;)).

My idea was to try one of the later JBL´s to, if possible, get more top end. But maybe the nice sound from the Altec 1" lies in the old alu diaphragm.....

[reVintage]

OK, checked some pics and on these aftermarket dia´s we can see that the bolt-pattern is mirror-imaged.


47207

[grumpy]

turn one around 180º :)

47208

[robertbartsch]

The Jim Lansing prototype diaphragms are true treasures.

Do we know, after leaving Altec, how many tooling dies Jim Lansing used to manufacture the first 175 diaphragms? I'm assuming it was only a few or perhaps only one or two tooling dies.

...just interested since my grandfather was a tool and die maker in Newark NJ about this time. Apparently, he did a lot of work for Bell Labs and others at the time. The name of his shop was Enterprise Tool and Die Co. He employed about 20 machinists.

[Steve Schell]

Thanks for the comments guys. I was given several of each type of diaphragm pressing by a member of the Lansing family a few years ago.

I am working on the assumption that there was only one 175 diaphragm tool for the first few years, as all the early diaphragms I've seen have that little flaw. It represents a small chip on the tool, as the diaphragms were pressed using a one part female tool. As I understand the process, a piece of foil is placed over the tool, then a rubber bladder filled with liquid is forced into the mold by either a press or a hammer blow. The D130 center domes were made this way in the early days with the hammer blow technique.

Robertbartsch, that is really interesting about your grandfather's machine shop. It is still routine in the speaker business for the engineer to make a drawing (CAD these days), then have a machine shop build the piece. JBL does a fair amount of prototyping with a couple of in-house rapid prototyping machines. Jim Lansing's ability to design something and immediately build the tooling himself and turn out examples had a lot to do with his tremendous output.

I am not sure of the differences between the Altec and JBL 1.75" diaphragm mounting. I do know that the positions and diameter of the locating pins are the same for the Lansing 801 field coil driver and the later Altec 802/804/806 etc.

Here are a couple of pictures of a 175 from ebay last year. I have seen many more like this. Notice anything unusual about the tangent down around 5 o'clock? The driver serial number indicates (I think) a manufacturing date of March 1953, which means that the chipped tool had been in use for at least six years by then.

[Steve Schell]

Here we go with the oversize pics again folks... sorry. This is an early 175 diaphragm I obtained from Hal Cox years ago. It was probably part of the load of memorabilia he obtained from William Thomas. I used to think that this diaphragm was a prototype due to the lathe turned bakelite and fabric ring, but later found that these were used until the mid 1950s. Imagine what it would cost to do that now! Anyway, we see the same tooling flaw, only this time someone has taken a small blunt object and pushed the flaw somewhat inside out in three spots. Note the lead out dress along the tangents, like the early W.E. 555W diaphragms. Also check out that beautiful edgewound aluminum voice coil, so perfect it looks like a single band of metal. The carefully made wooden box the diaphragm came in is typical of 1940s/1950s JBL diaphragm boxes according to Hal.

[Altec Best]

For real, Mike! Forget that Steve has pics of Jim Lansing's original work and prototyping. He has the really tiny details of everything, too. To narrow something of this age, down to that JBL probably used Jim's original tooling due to a little nib on one of the tangents, talk about a needle in the haystack!

And, I never even knew the tangents for the JBL spun in the opposite direction of the ALTECS!

Steve Schell, YOU are ONE INCREDIBLE INDIVIDUAL, and certainly one of the best LIVING ENCYCLOPEDIAS OF AUDIO I KNOW OF!



:applaud:


Where in the world do you find all this stuff Steve ?? I just absolutely love reading your posts this is a prime example of WHY !!! Super informative. And why Jim's suicide was a tragedy for everyone as he was one of the top genius's in the audio world at that time.Who knows what other innovations he could have brought to the audio world had he lived a full life.I just love the sound of any of the audio devices he thought of or improved upon and as why my favorite speakers have always been Altec & JBL .I hope you don't mind if I copy those pictures. Thank You for the info once again :applaud: Kind Regards ~ John

[spkrman57]

Thanks for sharing Steve!!!

Ron sends...

[scott fitlin]

My idea was to try one of the later JBL´s to, if possible, get more top end. But maybe the nice sound from the Altec 1" lies in the old alu diaphragm.....Well, I have my personal experience on this to add, FWIW!

My system originally used ALTEC 288 and 808 compression drivers with Aluminum diaphragms, and we changed to JBL 2441 with the 2395 lens horn in 1979-80. The ALTECS had a unique sound, that old fashioned TALKIE sound I used to call it, but Vincent Montanna Jr,s vibes used to sound amazing through the ALTEC horns. The JBL horns are incredibly dynamic and punchy sounding. BOTH are amazing sounding technologies of the past, and IMO still work today.

FFWD to today, a few years back, I bought the latest TAD compression drivers, the 4002 with neodymium magnets and their beryllium diaphragms. And it works and does EXACTLY what TAD claims it does. However, my problem, that I never realized would happen, is that it was TOO hot in the UPPER end, and the lower end response was not as punchy and full as the aluminum diaphragm JBL or ALTEC drivers. The problem for me, was that now with the TAD 4002 drivers, the top end in my room was too hot, and EQ and steeper roll offs didn't cure the difference to my complete satisfaction.

OTOH, I am right now installing the six TAD ET-703 tweeters I recently purchased, and I have already given them a whirl, and these have Samarium Cobalt magnets, Be diaphragms, and I LOVE THESE! They are, for me, the most extended tweeter I have ever used and/or owned.

And, just to let you know, EVERY TIME I change from the 2441 I still use, it completely changes the way the ENTIRE low end sounds in my room. For my own taste, the BEST sounding bass I get from my system, is when I use the JBL 2441J compression drivers. 3 years ago, when I had the TAD 4002 drivers on my horns, and I switched back to my JBL,s after two weeks, the bass, once again became so ferocious, and still very lively and had the best speed and detail. But, seriously, it was almost as IF I had doubled my low end acoustically, even though my compression drivers run 750hz to 7k, it affects everything above and below them. Really it does..

It was this experience that I understood what guys like Steve Schell, advocating the use of compression drivers on HUGE horns to reproduce bass, were talking about with things like his COGENT compression drivers on these massive horns to reproduce the LF in a music system for home hi fi playback.

Just another persons user experience.

[SMKSoundPro]

This is exactly why I am here on LH!!! Thank you Steve for sharing this info, and these stories. Everyone on the planet has heard of JBL the manufacturer, but I have never, NEVER heard or anyone say: "Jim!" Like he was just a regular guy. I have this iconic image of a great man akin to Howard Hughes in the movie "the Rocketeer" ("how do I look? - Like a hood Ornament!") to someone saying that's Jim over there at the lathe working on something. WOW!

ScottyJ, I know of what you speak. There is just something about it when it all comes together and when Steve pops up here with these archival artifacts of someone's craft... well that just blows me away. You would never see this on "How Its Made!"

Keep on, keeping on.

I have both Altec 1" and 2410 drivers and diaphragms here. I never thought to put one into another. I thought that might be like mixing Romulans and Klingons!

Scotty.
Wow, no really... wow! cool!

ps. Everytime I called Jenny in Northridge looking for parts, I would tell her I am on LH, and SHE would always answer: "OH, you're one of those Whackos!!!" whatever.

[Steve Schell]

I am a bit overwhelmed with the response to my additions to this thread. I guess I imagined that few if any folks would be interested in all the minutia. I'll try to contribute more of this kind of stuff until y'all tell me to scram.

SMK I hope I don't come across to some as casual or disrespectful for referring to the man as "Jim." I do feel like I have been able to climb into his head just a little bit, though he died fifty years before I developed an interest in his work. I have spoken to more than a dozen people who knew him, so there have been a lot of first hand stories to assimilate. I have also ventured into the world of loudspeaker manufacturing, so I have some idea of how tough it is. What I don't have is Lansing's skill or his drive; he worked practically non stop in his last years, trying to get Lansing Sound off the ground. His output was amazing despite all the obstacles, both in design and in production.

[Altec Best]

until y'all tell me to scram.
Well Steve that isn't going to happen I assure you.;) As I said in another forum that I wish you are able to stop by more often as I really enjoy the history you possess with audio in general and not just in Jim Lansing's endeavors.I really liked that post you had about the Altec field coil 601 with the handmade little multicell horn very cool.

I liken it to sitting around a campfire and listening to your stories about the history of Speakers,drivers,companies,JBL,Altec,etc.... Awesome !!

When I see your posts on the board they are one of the first I will read !!! :applaud:Just by reading your posts one can learn a great deal,so I would like to Thank You for that.Best Wishes to you ! Kind Regards ~ John

[SMKSoundPro]

@Steve,

NO, I don't think you're being casual or disrespectful! I have never thought of him as just Jim. My wife Lisa said last night in bed as I was telling her about these super cool photos and story that you shared, "well, I would never call Stuart Weitzman just 'Stu!'" (with her it's all about the shoes)

My comment is that I have never thought of Mr. James B Lansing as a Jim, as if I could just walk up to him and have a cup of coffee with him and find out what is in his head.

Thank you for altering and grounding my perception of him, and how dedicated he was in his craft. We are all the benefactors.

Sincerely,
Scott M. Koeller.
aka: One of those whacko's

ps. Please share more.

[tomee]

This is exactly why I am here on LH!!! Thank you Steve for sharing this info, and these stories. Everyone on the planet has heard of JBL the manufacturer, but I have never, NEVER heard or anyone say: "Jim!" Like he was just a regular guy. I have this iconic image of a great man akin to Howard Hughes in the movie "the Rocketeer" ("how do I look? - Like a hood Ornament!") to someone saying that's Jim over there at the lathe working on something. WOW!

ScottyJ, I know of what you speak. There is just something about it when it all comes together and when Steve pops up here with these archival artifacts of someone's craft... well that just blows me away. You would never see this on "How Its Made!"

Keep on, keeping on.

I have both Altec 1" and 2410 drivers and diaphragms here. I never thought to put one into another. I thought that might be like mixing Romulans and Klingons!

Scotty.
Wow, no really... wow! cool!

ps. Everytime I called Jenny in Northridge looking for parts, I would tell her I am on LH, and SHE would always answer: "OH, you're one of those Whackos!!!" whatever.

I too would like to thank Steve for sharing these stories and images! There's a handful of contributors here that make this place really special, and Steve is one of them for sure! If he's not working on a book about the early days of sound reproduction, he should be!

SMK - any chance you could try to put an Altec diaphragm into one of the 2410s you have? I bought a pair of 2410s that came with aftermarket Ti diaphragms in them and I'd really like to put in something made of Aluminum. Up till now I was thinking of Radian, but if Altec 1.75" diaphragms can fit, and seeing that the early Lansing 175 used a similar (identical?) tangential surround design (I never knew that...) I would prefer to try the Altecs!

[scott fitlin]

Steve, no one here is ever going to tell you to scram. You have some of the BEST information, pictures, literature, and knowledge of any one person I know of. You say this one thing that really sums it all up for me quite well! Feeling like "WE" have the ability to climb into his head and get an idea of what he was thinking. And if nothing else, your pictures, literature,and answers are ALWAYS extraordinarily interesting, but even more important, you always contribute HELPFUL answers and insight.

For me, personally, I am always intrigued by our past, and what was done and accomplished. I am familiar with some of the vintage audio treasures, and am always amazed at how good they were able to get things to work, despite not having todays technology, and machinery to create, and build things.

@ScottySMK, yeah, I know the feeling talking to someone at a company trying to get parts, and being told "Oh, your one of THOSE GUYS", too. But, IME, generally, we are usually speaking with someone considerably younger than ourselves, that may not really understand or even have knowledge of many of the products we seek parts for. And, when they are younger, and had no exposure to what we did, to them we are "WHACKOS" living in the past, as they only know the best of what they have been exposed to. What we do, it is hard to understand if you never experienced it.

[SMKSoundPro]

SMK - any chance you could try to put an Altec diaphragm into one of the 2410s you have?

Yes, I will try it today and post the results.

[reVintage]

OK, to get a clear technical picture, as noone has come up with any figures, I have ordered a pair of original, lightly used 2425 diaphragms to try with my 808´s.

Had some mail-correspondance with the seller with various measurements. He mentioned he once had used 2410´s without modifications in his Altecs, but I find it unlikely.

It seems like the the difference is that JBL has a 67mm hole-pattern radius as Altec has 68mm. But this will be easier to check when I get them. Will then make a drawing.

[reVintage]

No walk in the park to fix this but I´ll give it try.

The bolt/pin-circle dia is bigger on Altec. Found an earlier thread about this too. Earl K had found out he same as me. The difference is 68mm to 67mm.

EDIT: Measured once more and the difference at the pins is actually 1,5mm measured over both. This means we have to ovalize each hole 0,75mm.

Anyhow the bolts and pins are in the right place relative to each other.

Have check this with a pair of used original 2425 that I bought to a very reasonable price.

Will try to find out how ovalize the holes and still keep the centering. Think I have a solution!

[louped garouv]

Will try to find out how ovalize the holes and still keep the centering. Think I have a solution!

:applaud:

[grumpy]

Think I have a solution!

Yes, a sine wave generator and those funny appendages on either side of your head! :D
(I wouldn't count on elongating the bolt-hole clearances radially to do the job)

Hope it goes well :)

[reVintage]

I wouldn't count on elongating the bolt-hole clearances radially to do the job



So what would the problem be if one can measure the elongation on each side with the precision of 1/100 mm? But tone-generator and ears might be needed if that fails.....
Will anyway check the theory on a pair of cheap aftermarket diaphragms.

Anyway I had to return the 2425 diaphragms as one of them had two small dents on one of the domes. Good thing though, I had them long enough to do the measuring needed.

[grumpy]

So what would the problem be if one can measure the elongation on each side with the precision of 1/100 mm?

... the assumption that the original machining/molding/etc... was that good to begin with,
especially with "cheap aftermarket diaphragms."

It may very well work fine, and I certainly hope it does, I just wouldn't depend on it 100%...
anymore than I would -completely- depend on the original locating pins. I did not mean to
discourage your investigation/experiment.

Best regards.