Steve , Wow! What a great posting ! Thank-you so very much for this !

- The insights into the actual construction of the driver ( and diaphragm ) are just priceless & of course the pics .

- I do hope you get your tweeters going sometime / though I understand given these units rarity, if it's a one time happening .

- Don't field coils benefit from smoother DC than what can be provided by 1/2 wave rectification ( or have I missed mention of other smoothing components ? )

Cheers ( I love the formulas for the derived mechanical constants )

ps : I wonder if Tool & Die workers these days still offer the better "one-off" approach by being able to use "spun" product soft-pressed into a die / as compared to hydro-forming or heat-pressing . Of course , I would have liked to know the gauge of the wire used for the voice coils and the total length of the windings as well as the gap width ( but I'm just a junky for that sort of info ).