Manualblock,
I actually have the schematic for the model 19. The 2nd order low-pass section is set for 500hz if you take the values and compare them to Pi 500hz crossover for the bottom end. The high-pass section is set for around 1.5Khz with a slightly different HF attenuation/compensation network from the Pi crossover. The midrange control is only a coil paralleled with a potentiometer in series with the ENTIRE crossover at the input. If the pot is closed (shorts the coil), the coil is effectively removed from the circuit, if the other extreme, you have a .3mh coil in series with your crossover. Cute, but I question the wisdom of the midrange circuit control in this.
In reality, the basic crossover for the model 19 is really just a 2nd order low-pass at 500hz and a 3rd order hi-pass at 1500hz. I am going to use the Pi 500hz low/1.6khz hi and result in the same, I feel no need to run the system through a coil(mid control).
I bought the 416's from Great Plains new, but now I regret as I prefer the JBL 2226's for their design: natural rolloff at 2khz/20db, not need for fancy crossover or zoebel, and their bass is lean vs the 416, but seems to have a flatter response(at least to my ears that is!!). Also, Altec finally figured out after many years to use a 9 cubic ft ported box for the 416. Many Valencia/Flamenco versions were ported 5.7 cu' designs, and that was very liberal if you actually measure the internal dimensions.
For your project: Use the 2226 w .7 mh air coil(biggest wire guage you can afford) and 1.6khz high pass(parts express), R2=15 ohms, R1=30 ohms and .47 ufd cap. That is for 802 on 811B horn. Also, look what Bill mentioned about metal Altec horn becoming less annoying(ringing) when mounted at the front flange, dampens well enough to tolerate. I myself got sucked into wooden horns and will never go back!!!!
I hope this helps, if not better experts than me will show you the way!!!
If you need anymore info, send me a private e-mail
Regards, Ron