Just wanted to pass this along, I contacted ZXPC and was informed the diaphragms are made by LASE, supposedly a USA company. I found this website:

LASE

All Products

They list an Altec section, but it only states that new products are coming soon.

The seller is supposedly in Florida and signed the response "Mei" The email began "good morning", but it was 1:26PM EST for us both (if in Florida)