The impedance is not important if as you say you plan to use 'Active' electronics. A realistic figure for each group of strings would be about 3.75kohms it may be harder to get more out of a pick-up the size of just three strings, but, I'm NO expert, Ron is. Ask him I know he can do it and I know that he will take pride in his work. He is the premier steel guitar builder in the UK and has been for 25 + Years.
I don't subscribe to the theories bandied about regarding better tone + Higher impedances of 15 - 20k, just measure the pick-ups on pre-war lap steels, some of them are hardly 3k, YET they sound 'Warm' .. the number of Windings - wire gauge - type of magnets and positioning of the pick-up are all variables that have more or less affect on the tone.
Have you hard of 'John Birch' Electric Guitars ?
well I pushed John into pick-up manufacturing that eventually led to him setting up his guitar company.
When he was a service technician for Ampex VTR's he and I used to experiment with pick-ups and we modified the Fender 1000 that I recorded at Abbey Road Studios with. we also put a Pick-up on my Hofner Golden. I've been messing with pick-ups a long time.
The ones I made for this guitar were 'Liberated from Public Telephone boxes in the early 50's and I used the coil and magnet assembly that drove the 'phone's diaphragm. Each pair of strings had a 'phone magnet assembly and they were wired to balance pots and then through a low to high mike transformer in the guitar.
So I Do know what you're trying to do.
<font size="1" color="#8e236b"><p align="center">[This message was edited by basilh on 17 June 2006 at 12:58 PM.]</p></FONT>