Just a couple of late remarks on the speaker drive units:
The NAD 8200 looks absolutely identical to the Fried Signature Series Model A, with a Seas 21F-EWF woofer and a Seas H140 tweeter (customer-specified versions of the 21F-EW and H086, with silver finish instead of the standard black). The letter F added to the woofer name would be a reference to the customer, as per Seas' naming conventions; in this case Fried. Therefore, I'd bet rather confidently that the NAD speaker is a rebranding.
Although the image in the original post is a bit blurry, this large 3-way model seems to have the same H140 tweeter, possibly accompanied by versions of the Seas 25F-EW woofer and 13F-GMB midrange, the latter of which would have a foam surround. The drivers will usually have a sticker on the magnet, with model names and week/year of manufacture, and I would expect these to be from around 1978, give or take a year. The "tunnel loading" TL port, typical of Fried's speaker designs, is also visible at the bottom end of the front. Since the label reads "Fried Signature Series", it probably predates the NAD-branded speakers, if such a NAD model did exist (I haven't been able to find images of the 8300 anywhere, at least so far).
The H140 tweeter features Seas' characteristic punched-out circular pattern on the front plate, which constitute the actual centering mechanism for attaching the magnet system to the front plate/dome assembly (this was originally invented for the H086, and used on all 1" tweeters until the mid-80s). The domes are hand-coated textile, with a "catenary curve" profile (similar to the pointy end of an egg, if you like). The protective grid is held in place by 4 screws. These screws also hold the magnet system to the front plate, so never attempt to unscrew them while the tweeter is mounted in the enclosure!
Seas didn't start making their own metal dome tweeters until the late eighties. By this time, they had also mostly transitioned to molding their front plates/dome assemblies from fibreglass-reinforced plastic. Some OEM customers still needed the old units, though, so the old manufacturing tools were still kept busy. Seas did supply Acoustic Energy for a period too, and AE went with a slightly modified version of the older stamped-metal front plate design, presumably for better rigidity. I don't have a complete overview of AE speakers, nor their history, but some models - perhaps early ones - seem to be fitted with Elac tweeters instead. Those tweeters are recognized by a smooth front plate surface, with two small centering pins on the magnet protruding through it.
The Seas-made AE tweeters retained the classic centering mechanism (not particularly pretty, but it's there for a reason). A protective grid made from rather delicate mesh, not much larger than the dome itself, was added, just like on the Elac tweeters. This grid fit into a groove in the front plate, and was held in place by magnetism and a dab of glue. AE opted to leave the "phase plate" out, though. This was a 12 mm diameter transparent plastic disc, glued to the inside of the grid in front of the dome on standard models. While the characteristic
metal dome peak above 20 kHz would be equalized by the phase plate, the technique possibly introduced other problems. Note that the assembly screws on the AE tweeters are located at a larger distance from the dome, compared to the older H140 tweeters. This is because Seas' magnet systems had to be redesigned for the introduction of molded plastic front plates/dome assemblies.
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