Altec 2-way XO update

The Altec N1600C series crossover has been a significant constituent in the evolution of my Altec 2-way horn speaker system. C. G. McProud's 1947 article on page 101 of Audio Anthology, Volume 1, was my first encounter with series crossovers although Western Electric was already using the topology in the 1930s. As an aside, my knowledge of electronics is basic. I don't even own a circuit simulation program and rely on my collection of audio electronic textbooks, old magazines plus what my ears tell me as reliable internet sources for "techie stuff."

JEL/N1600C 2-way Crossover

Based on Earl K's simulations and analysis at the Lansing Heritage forum, Altec configured the N1600C 2-way crossover with staggered filters. In this application, a 2nd order/12dB/octave high pass filter @ ~ 1600 hz is provided by the 4 uf capacitor + 1mH inductor, while the 1mH inductor series connected to a 16 uf capacitor functions as a 1st order/6dB/octave low pass filter @ ~ 1100 hz. The 30 ohm potentiometer is part of an upper midrange frequency attenuator/high frequency EQ boost circuit I derived from reading through Altec 30923 discussions at Audio Karma and at Lansing Heritage. Altec incorporated this circuit in their Model 19 crossover and Jeff Markwart used it in his phase corrected Altec 605 crossover. 

In subjective terms, the combination of staggering the crossover point + upper midrange attenuator creates a "dip" in the crossover region where harshness and congestion can easily be detected by critical listeners, while my Altec 3000H tweeters were made redundant by the high frequency EQ boost.

Outboard crossover built using
paper in oil caps, low DCR air core chokes and
non-inductive resistors