AFAIK, all 414's used a cast frame. The early cast frames had curved spokes. 414z will be painted gold and have no magnet cover. 414A will be painted green with a can/cover over the motor. 414-16B/414-8B use the same motor in a newer style square spoked frame. 414-8C/16C use the one piece cast steel 416-8B type motor structure on the newer frame.

It's possible some very early 414's may have used the stamped steel frame of the 600B, but i cannot find an example.

IMO, the 414 "C" version produces the best midrange of any Altec woofer.

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