Altec 604 C diaphragm differences - Help

[HeathKitPat]

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.

[zelgall]

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.

[magnarc]

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.

[cradeldorf]

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

[bowtie427ss]

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

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

[Old Guy]

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.

[cradeldorf]

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

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

[rontec]

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

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.

[HeathKitPat]

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

[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.