Altec 604 C diaphragm differences - Help

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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...