Difference between Altec diaphragms

[bowtie427ss]

I'm also wondering if the symbiotik were enough higher in compliance, that phase plug contact was only an issue with them, and not so with the aluminum and pascalite diaphragms.

I'm using the GPA 26420, i didn't buy them directly from GPA, but i think it's safe to assume that they kept the numbers the same and these would be pascalite.

[Old Guy]

Originally posted by bowtie427ss:
I'm also wondering if the symbiotik were enough higher in compliance, that phase plug contact was only an issue with them, and not so with the aluminum and pascalite diaphragms.

<font size="2" face="Verdana, Helvetica, sans-serif">Don't know for a fact, but common sense would bear you out.

[sguttag]

There is always a tolerence in the manufacture of diaphragms and compression drivers. Some manufacturers include shim rings with their diaphragms rather than scrap the diaphragm (Radian comes to mind). I don't recall ever having a shim ring on any of my Altecs but I don't doubt that they did exist.

JBL, has a nifty coding system, if you know where to look for it. They have a +/- 3 scale. Ideally, you want the same number on both the diaphragm and on the driver...what you don't want is a +3 driver with a -3 diaphragm. This, of course, requires the manufacturer to measure each driver and diaphragm.

[RonSSS]

Bowtie427,

Years ago Jim Dickenson told me that the 802-8G diaphragms were special and made of an extremely thin aluminum. He sai "don't blow them up" because original replacements were not available. This was 20 years ago.
The 802-8G has a unique diaphragm part number.

That said, if yours are original and working, I wouldn't mess with them.

The 909 pascalite diaphragms are excellent units and were what Jim recommended as replacements for all of the small format drivers.

I have both a set of original 802-8G's and 2 sets of 902-8A. I actually prefer the 902 drivers.

BTW......427 is kinda small these days!
Maybe I should change my name to Bowtie496.......

Forgive me, I'm a rat motor freak and have a 69 496" Nova street car that run's high nines N/A.
Fun stuff!

Ron

[Old Guy]

There is a very lightweight diaphragm you can't get anymore. Very bad about reliability though which is why you can't get them.

Arguably the best 3 American V-8's were produced as competitors in the 60's.

Ford and Chevy 427's and the Chrysler 426 Hemi.

I have a side oiler Ford I'm saving for "someday".

One of my relatives has one of the original Nascar only 427 Chevys from prior to the ones you guys know and love. Parts are a problem because it is a bit different from production models.

The 427's were in Nascar some 4-5 years prior to the Corvette.

The reason I'm not including the original Chrysler Hemi is that most of the ones that did anything were mostly made of aftermarket parts, not the original factory ones.