Graphite diaphragm?

What is this?

Vintage Altec Prototype Graphite Horn Driver Diaphragm, 802,804,806,808,16 Ohms, | eBay

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Attachment 4582Attachment 4583

Might be a workable concept, but not sure what the picture is. Looks like a plastic protective cap with felt, offset to the left. Lead wires appear to go over the cap, so maybe it doesn't come off. Maybe the wires to retain the plastic cap, and real connections below the cap,

Pretty badly presented item - not so uncommon on eBay. Perhaps useful to contact the seller and ask for more pictures. Someone good with tech is not always good at communication and sales......

Yeah I’ve just never heard of such a thing. I know about materials like paper, phenolic, Mylar, aluminum, titanium, and beryllium for diaphragms, but I’ve never heard of graphite being used.

Maybe you’re right about it being just a cover that peels off. The seller certainly makes it sound like it’s some kind of special prototype graphite diaphragm though. Haha

Interesting! Seen graphite microphone diaphragms, so implies that they were (are?) trying to create a large variant of the 3000H.

edit: then again.......34726 is GPA's listing for 8 ohm Symbiotik, so caveat emptor applies big time! :mad2:

Ok so I contacted the seller. He claims to be a friend of the person who started GPA (assuming Bill), and said he got the diaphragms from him. 40 years ago. He said they were testing different diaphragm materials and these were prototypes

He said he has a pair, one working and one not.

Thanks! Considering the advances in metallurgy in general and specialized diaphragm design, coatings since then combined with Altec's decline to boutique status at best, not even worth $65 to me.

I'm certain the seller knows somebody.

The auction ends soon and no bidders yet. I don’t need any more “conversation pieces”

We’ll see if it even sells.

If you have the 'patience of Job", then recommend experimenting with this tweak: EnABL

https://www.diyaudio.com/community/threads/learn-to-enabl-speakers-with-products-available-in-eu.409783/

https://pearl-hifi.com/06_Lit_Archiv...hragm_Mtls.pdf

Thanks for the reminder! :Thumbs up::Thumbs up: