After much serching I found the details of the passive crossover I used with my 511b, 2x416a IB setup I built many years ago. The design comes from Audio Magazine, November 1969 issue. Using iron core mil spec inductors and a few resistors & capacitors it was fairly inexpensive when built. I had the added bonus of an employee discount from the distributor I worked for at that time.

I have scanned the article in high resolution B&W, but the file size for each page, one of the cover and three of the text are still in the 2.5mb each, range.

Should anyone want to go to their local library & try and find it for their own education, I'd encourage it. Otherwise, if you're an electronics whiz, you might just find it entertaining. My own library

Dialup internet service makes it a lengthly process to send here, although I could try, but it would require 4 full screens to display. I would not object to sending out a few copies my snail mail.