Altec 604 C diaphragm differences - Help

A friend stopped by today to give a listen to my 604c's for the first time. I consider him very well versed in most aspects of vintage audio especially the 604c. He is the person that guided me down the path that led me to where I am today. After a good listening period he told me that he believed I had two different frams.. since both were an original pair that came from the original owner and both were untouched (the red paint on the screws was unharmed) I questioned this. He said there there were actually a few different versions that the factory installed with one being especially good. It depended on production date. Both of these are 1957 604's.. he stated that it could have been even a matter of weeks or even days from one fram to the next in production. This sounds possible.. According to him I have one of the especially good ones which is not to say the other isn't great too. His exact words were Stellar and super Stellar..

Can anyone add information regarding this? I'd love to hear about it.

Not to disagree with an expert but I think you'll find that most of the discrepancies in Altec parts and cones in particular came from the late 70's to the end of the road for Altec. They used whatever parts were available to make the model. There are 416's with white frames, 604-8g's with and without front accessible horn mount screws etc.
I'm a big fan of Altec and have 19's and 604-8g's, both of which are the end of the trail for me.

With diaphragms that age, fatigue is likely to be the reason for difference, not different types.
Minor manufacturing differences, even slight tolerance differences, can amplify to possibly audible differences 50+ years later.
I'd say they will be part number 20275 diaphragms, the 16 ohm 1 inch.

The point? Do they sound great to you? If yes, then who cares what someone else thinks.

Make sure it's not the amp balance being off slightly or something simple like that.

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Can anyone add information regarding this? I'd love to hear about it.

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The same diaphragms show up in 802B's, they've become as rare as the old timers who knew about them.

A little knowledge is a dangerous thing, and that is what he seems to have. Not that his info is wrong, he just doesn't know the full story. If you have original frams, there is only ONE design. The "good" one he is talking about was made 20-25 years AFTER your speakers. I suspect it's either fatigue, as mentioned, or an electrical issue if they sound different.

Is it possible that undocumented changes were made?

We had a friend, actually my older brother's friend met through another "hobby", who was a for many years a projectionist in the SYR area. His audio/radio collection was my first listening experience with a large format Altec speakers, had a lot of "firsts" at his place beginning in the late 1980's. First and only place i've ever seen an amplifier that used thoriated heaters in some of it's tubes, kinda shocking to see that much light come from a tube heater.

Anywho, this fella (Art) was always seeking 802B's for their diaphragms, i'm sure he made some off handed comments about "why" but i never had the awareness to have any depth of interest in that stuff when we were making trips up there. While i'd been exposed to Altec consumer stuff as a child and teenager, and lived with model 17/604-8G from the late 70's into the early 80's, my interest never became passionate until the late 90's when introduced to the internet and ebay.

Maybe his motives were based on ancient urban legend or pure myth, but my recollect is that he wanted 802B's specifically. "The rough paint, they gotta have the rough paint, if they're smooth they're no good" is what i distinctly remember him saying. I wish he were still with us, or my visits more recent.

I have also heard/read others desire and preference for undisturbed 802B's, but never accompanied by an explanation of "why".

Sorry, i can really only add to any mystery.

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Originally Posted by cradeldorf

Make sure it's not the amp balance being off slightly or something simple like that.

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My thought exactly! Vintage amps, crossovers, components, etc. I would swap the speakers just to make sure the "super stellar" is really the one. But if you don't hear a difference to begin with...why bother.

Further discussion with my friend today about the frams involved a feeling from him that late production 604c's had frams that were special by accident. Something about the metallurgy and they way the material from the supplier came through.. He also said they have a different part no. I have not cracked open the drivers to confirm. These are untouched so I don't plan on doing it. This afternoon, I had some time to play and picked out a few albums that had excellent bell ringing sections.. doing an A/B test in mono with the speakers being switched back and forth from amps. There IS a slight difference. The one speaker he stated as having the stellar fram does have more sparkle. I bought this pair of speakers from the family of the original owner. He purchased them NEW as a pair in late '57 for his audio service/sales shop. This was a backup pair in case anything happened to his main pair (four purchased at the same time).. These speakers saw very little use. They are pristine and untouched both with 1957 stamped on the basket. I am using a Fisher 400c and a pair of Heathkit W4's that I rebuilt as twins and have hotrodded and upgraded to use 6L6GC's.. a matched quad of new tubes from Tube Amp Doctor. So for all intents and purposes we have matching amps. All listening tests were done in mono.. so without question the one 604c has more sparkle (super stellar).. the one that doesn't still sounds stellar! But there is a minute difference. Anyway, I'm not trying to be nit picky, I absolutely love the sound of both speakers.. I was just hoping someone could confirm these findings or expound on it more. I love the history behind these things and if there is information out there it's great to keep it alive. Thanks, Pat

The motor in the one could be a little weaker as well... They are 50 years old.. They could probably both use a re-magnetization. You will never really know until you open them up and check the diaphragm part numbers to confirm.

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Originally Posted by bowtie427ss

The same diaphragms show up in 802B's, they've become as rare as the old timers who knew about them.

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Probably explains why was mine missing after it went to GPA.

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Originally Posted by Altec Best

The motor in the one could be a little weaker as well... They are 50 years old.. They could probably both use a re-magnetization. You will never really know until you open them up and check the diaphragm part numbers to confirm.

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Although this is quite possible, they are both 1957 production dates and they have been together since new which means they were exposed to the same atmosphere, storage, usage etc.. I would hope that even if a little weak that they are equally weak.. If they came from two different sources I would be more inclined to go along with this theory. :p

Also given that these are pristine 604c's with original cones in excellent condition they will probably never come back out of my 606 cabinets and definitely will never make any kind of journey in a shipping crate anywhere to get remagnetized. eek: I'd be too afraid of something happening to them. Only way they will ever have the luxury or demagnetization is if I can drive them somewhere myself..

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Originally Posted by cradeldorf

Probably explains why was mine missing after it went to GPA.

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If I sent a speaker out with a perfectly fine diaphragm I think I would get the old part back!! especially given the rarity and price of an original fram!

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Originally Posted by HeathKitPat

Although this is quite possible, they are both 1957 production dates and they have been together since new which means they were exposed to the same atmosphere, storage, usage etc.. I would hope that even if a little weak that they are equally weak.. If they came from two different sources I would be more inclined to go along with this theory. :p

Also given that these are pristine 604c's with original cones in excellent condition they will probably never come back out of my 606 cabinets and definitely will never make any kind of journey in a shipping crate anywhere to get remagnetized. eek: I'd be too afraid of something happening to them. Only way they will ever have the luxury or demagnetization is if I can drive them somewhere myself..

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If I sent a speaker out with a perfectly fine diaphragm I think I would get the old part back!! especially given the rarity and price of an original fram!

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I can assure you they'll never see my business again, The only reason I sent it was in case they needed to be rebuilt so they would both sound the same. Over 500 bucks in shipping, took at least 4 calls to them to get them on their way back home. They were done the first time I called, three weeks later I was still calling. and in the end I see the phram replaced in the one I told them had nothing wrong with it. just my .02

All this phram talk got me wondering about what I have in mine. I have 604Ds which are similar to late model Cs. I popped the cap off the back, but didn't have time this AM to go further.

These are my phrams:

http://www.hostboard.com/forums/hbmc...2013/03/26.jpg

Is there a number printed in the other side? Can I remove it safely?

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Is there a number printed in the other side?

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Probably a silver inked "L1" next to the terminal connected to the outermost winding of the voice coil. I wouldn't expect to see anything on the topside unless it was a later pascalite, those had "909" and the maestro inked right on the aluminum dome, i'm betting you've seen them before.

Some part numbers were stamped on the inside circumference of the paper voice coil former

http://i107.photobucket.com/albums/m...sympasfrnt.jpg

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Originally Posted by cradeldorf

Probably explains why was mine missing after it went to GPA.

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Sorry to hear of this. I feel fortunate that i was advised long ago to NOT send working diaphragms or salvageable cones when having anything rebuilt as you will not see them again.

It is also a good idea to tape a note to each component specifying the exact work you want done to it. There's just no substitute for good communication.

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Originally Posted by bowtie427ss

Probably a silver inked "L1" next to the terminal connected to the outermost winding of the voice coil. I wouldn't expect to see anything on the topside unless it was a later pascalite, those had "909" and the maestro inked right on the aluminum dome, i'm betting you've seen them before.

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So is there any way to discern which diaphram it is? Not that I care all that much, but since we were on the subject...

Process of elimination. Once you examine the knowns, impedance, material, terminal type, the possibilities become pretty limited.

I often wonder what changes in the alloy, it's hardness, and it's thickness may have taken place over the years. I'm talking about un-documented changes, and even changes that Altec might not have been aware of until well after the fact. Since Altec never owned an aluminum smelting/processing plant(that i'm aware of), they would have been at the mercy of their supplier where contents and consistency of the diaphragm material was concerned.

Hindsight being 20/20, i wish i'd had the inclination to measure the thickness of all of the vintage diaphragms that have passed through my hands. Sadly, i have divested myself of nearly all Altec product manufactured before the mid 1970's and have only modern Altecs remaining.

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Originally Posted by HeathKitPat

Although this is quite possible, they are both 1957 production dates and they have been together since new which means they were exposed to the same atmosphere, storage, usage etc.. I would hope that even if a little weak that they are equally weak.. If they came from two different sources I would be more inclined to go along with this theory. :p

If I sent a speaker out with a perfectly fine diaphragm I think I would get the old part back!! especially given the rarity and price of an original fram!

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Even speakers just manufactured in sequential order will have slight variations especially with Alnico... No 2 Alnico magnets will hold the same charge,they will all have slight variations.IMHO.. Just putting power through them will weaken a motor especially after 50 years and if the volume is quite high it will weaken them even quicker..

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Originally Posted by cradeldorf

I can assure you they'll never see my business again, The only reason I sent it was in case they needed to be rebuilt so they would both sound the same. Over 500 bucks in shipping, took at least 4 calls to them to get them on their way back home. They were done the first time I called, three weeks later I was still calling. and in the end I see the phram replaced in the one I told them had nothing wrong with it. just my .02

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That is a shame since they are the only place to get original Altec parts.I have posted this several times on this board before..If you send in your drivers to GPA for a rebuild ? No care will be given to the old diaphragms.I posted this about 802-8G's and the lite diaphragm 23744.. Bill doesn't keep them he throws them out..he manufactures new ones..

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Originally Posted by alancohen

All this phram talk got me wondering about what I have in mine. I have 604Ds which are similar to late model Cs. I popped the cap off the back, but didn't have time this AM to go further.

These are my phrams:

http://www.hostboard.com/forums/hbmc...2013/03/26.jpg

Is there a number printed in the other side? Can I remove it safely?

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Yes on the inside lip underneath there should be a 5 digit number. This is the model #

Look here Alan this is a 23744 diaphragm.

http://www.hostboard.com/forums/hbmc...2013/03/27.jpg
HPIM2345 by Altec Best, on Flickr

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Originally Posted by bowtie427ss

Sorry to hear of this. I feel fortunate that i was advised long ago to NOT send working diaphragms or salvageable cones when having anything rebuilt as you will not see them again.

It is also a good idea to tape a note to each component specifying the exact work you want done to it. There's just no substitute for good communication.

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Exactly ! I posted this awhile back myself.. If you want to keep your old diaphragms it's best to take them out first before sending them anywhere.. Bill himself told me several times to put a note in the package on what you want done..He has so much work if there is no note he will just rebuild the whole driver,woofer,etc...

You post what you want done.Record all pertinent information and write it on the note.Copy one for yourself..I used Wordpad and printed 2 copies one for me and one for Bill and never had a problem.. The only problem I had with GPA is it took 2 months to receive a pair of 416-8B's one time that he had to recone due to failed spiders from storing face down for many years.

Always record serial #'s too.. :wink2:

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Originally Posted by Altec Best

Look here Alan this is a 23744 diaphragm.

http://www.hostboard.com/forums/hbmc...2013/03/27.jpg
HPIM2345 by Altec Best, on Flickr

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Ah-ha! I'll look when I get home. I'm OK removing a few screws to find out, just not dislodging things that need special tooling to reinstall. I'd like to know, but not that much!

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Originally Posted by bowtie427ss

Is it possible that undocumented changes were made?


Anywho, this fella (Art) was always seeking 802B's for their diaphragms, i'm sure he made some off handed comments about "why" but i never had the awareness to have any depth of interest in that stuff when we were making trips up there. While i'd been exposed to Altec consumer stuff as a child and teenager, and lived with model 17/604-8G from the late 70's into the early 80's, my interest never became passionate until the late 90's when introduced to the internet and ebay.

Maybe his motives were based on ancient urban legend or pure myth, but my recollect is that he wanted 802B's specifically. "The rough paint, they gotta have the rough paint, if they're smooth they're no good" is what i distinctly remember him saying. I wish he were still with us, or my visits more recent.

I have also heard/read others desire and preference for undisturbed 802B's, but never accompanied by an explanation of "why".

Sorry, i can really only add to any mystery.

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Altec DID sometimes source from different manufacturers. Perhaps whoever supplied materials? The 802b fram likely was hand assembled with care. Beyond that, no clue. Odd how it works out, the 288G brings a higher price but IMHO the 288H is a better driver...

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Originally Posted by bowtie427ss

Sorry to hear of this. I feel fortunate that i was advised long ago to NOT send working diaphragms or salvageable cones when having anything rebuilt as you will not see them again.

It is also a good idea to tape a note to each component specifying the exact work you want done to it. There's just no substitute for good communication.

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I bear some of the responsibility as I did not send info in both boxes as to exactly what I wanted done nor did I include pre paid return labels. So not entirely bills fault.

My phrams don't have any numbers on them:

http://www.hostboard.com/forums/hbmc...2013/03/28.jpg

http://www.hostboard.com/forums/hbmc...2013/03/29.jpg

These had been sent to Bill for "the treatment". It's possible they got new phrams as well as new cones. The good news is everything should match nicely. The better news is I got some pretty good cabs with them, so all in all, a great deal for $1125. Now if I can just figure out this crossover dilemma...

New phrams would be stamped with a date right where your 391227 is. The one they replaced in my C had a date of April 11 2011 or something stamped there. sorry yours says 511227... I would think it would be a 391 number... anywho I found this one on ebay same as mine pretty much.

I think that 511 number may be from the later era.

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Originally Posted by Old Guy

I think that 511 number may be from the later era.

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Yeah, supposedly the 604s were in the catalogue only in 1957 and were replaced by the 605s in 1958. After that they were still made on a custom basis, mostly for studio customers. No telling what year they came from. When did the 604Es come out?

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Originally Posted by alancohen

When did the 604Es come out?

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1964-ish. They weren't really custom, anybody could get them, they were just not advertised heavily as Altec was pushing the cheaper-to-build 805.

http://www.hostboard.com/forums/hbmc...2013/03/30.jpg

http://www.hostboard.com/forums/hbmc...2013/03/31.jpg

Where does the "D" fit in then? I think it was "C" till 57 and "D" to 63.
My "E" is stamped 64.

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Originally Posted by cradeldorf

Where does the "D" fit in then? I think it was "C" till 57 and "D" to 63.
My "E" is stamped 64.

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As far as I can tell, the Ds were in the catalogue in '57, gone in '58 and replaced with 605s. You could still buy a 604D if you knew about them. I'm guessing they made the "604D" until the "604E" came out. So the 604Ds were 1957-1963 mostly as a special order only since they were not advertised.

Someone just got a deal:

http://www.ebay.com/itm/Altec-lansin...item3f22ab7442

After further review: a 1958 ad that shows 604Ds

http://www.ebay.com/itm/Altec-Driver...p2047675.l2557

I talked with Bill Hayes today, who'll be 90 this July incidentally, and he says that there was never any diaphragm change in the production model of the 604C.

Any differences, he said, would be due to the fatigue of the diaphragms, plus weakening of the magnets. It could also be the crossover(s).

Is the room perfectly symmetrical?

Hi Todd, great to see you.

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Originally Posted by alancohen

My phrams don't have any numbers on them:

http://www.hostboard.com/forums/hbmc...2013/03/28.jpg

http://www.hostboard.com/forums/hbmc...2013/03/29.jpg

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No yours won't if they are GPA's.. Those numbers on the inside lip of the voice coil are Altec part numbers

Thanks, OG!

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Originally Posted by Todd W. White

I talked with Bill Hayes today, who'll be 90 this July incidentally, and he says that there was never any diaphragm change in the production model of the 604C.

Any differences, he said, would be due to the fatigue of the diaphragms, plus weakening of the magnets. It could also be the crossover(s).

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Hi Todd, sorry I don't know who Bill Hayes is? Was he an Altec employee or an Altec engineer? What I was told is not so much a change in the design but rather a change in supplier of the materials used to manufactur.. a better metallurgic mix if even by accident. Now I'm not sure if this is Urban legend or what.. just digging for confirmation/information. As to crossovers they are new GPA manufactured xovers designed by them for use with the 16ohm 604's. The listening tests were conducted with my face planted squarely infront of the speaker about a foot away.. moving back and forth between speakers and replaying certain passages over an over again for comparisons sake.. all other factors are the same. Speaker leads were swapped back and forth between mono block amps etc..

also in regards to magnetic loss.. this is copied from audio asylum forum and I have read and heard much the same elsewhere.
Actually, if not abused, they should last almost forever. After a magnet stablizes, the loss of magnetic strength is on the order of 1% per thousand years. Its rare for loudspeakers used in a home environment to be run at the levels that would cause demagnetization of the magnets. This is usually only seen in commercial venues that run systems at full rated input levels for long periods of time. And even then, its not as common as you would think, going by all of the repeated mis-information you always find on the internet. Take your loudspeakers outside, away from sources of reflections, and feed them the same input level with a signal generator, and measure the sound level of both, from the same fixed distance. If they measure reasonably close to each other, I would not worry any more about it.

another copy paste on the same subject..

Google up Alnico or Cobalt You will soon read that Alnico is projected for a 2,000 year Life before mag field Fluz degradation is significant.
ANYONE selling/pushing Re-Zap is either a Fool or just wants yer $$.

Bill was Director of the Acoustic Laboratory from 1958 or so through 1983. He was also an employee there from the late 40's, and worked for John K. Hilliard and Alex Badmaeiff. Brilliant, yet humble guy.

He said they routinely tested the diaphragms and would have noticed any measurable changes.

I don't care what the Audio Asylum (aptly named) folks say - Alnico V magnets used in speakers DO lose magnetism over time. This is measurable and can be easily demonstrated.

This is one of the best things about AUB - these wonderful factoids from the people who know.

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Originally Posted by HeathKitPat

ANYONE selling/pushing Re-Zap is either a Fool or just wants yer $$.

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There are some holes in your reading. Alnico CAN be discharged by impact. Most writers are NOT engineers, and don't fully understand things. Add to that that even among experts there are differences in opinions. Life is not cut and dried. My engineering degree did teach me that there is way more to learn. The fool is the one who thinks he fully understands an extremely complicated universe.

GPA does not charge for remag when reconing AFAIK.

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Originally Posted by HeathKitPat

ANYONE selling/pushing Re-Zap is either a Fool or just wants yer $$.

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Originally Posted by Old Guy

There are some holes in your reading. Alnico CAN be discharged by impact. Most writers are NOT engineers, and don't fully understand things. Add to that that even among experts there are differences in opinions. Life is not cut and dried. My engineering degree did teach me that there is way more to learn. The fool is the one who thinks he fully understands an extremely complicated universe.

GPA does not charge for remag when reconing AFAIK.

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No they don't.. Re-mag is free with a recone or a diaphragm replacement. I have a couple pair of 416's that benefited from re-mag. :smile2:

I would think Heat would be another factor that can degauss a magnet, but don't quote me.

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Originally Posted by cradeldorf

I would think Heat would be another factor that can degauss a magnet, but don't quote me.

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Google "Curie Temperature". :D