Granny,
Why not bias the electrolytic caps in the woofer cross over all you need it two (4 for the set) more 1000uF capacitors which Madisound sells, put them in series with the existing capacitors then bias the mid point with a number of 9V batteries in series, four should probably do for 36V. Positive goes to the midpoint via a 1M Ohm resistor negative goes to ground. JBL use this technique in their flagship speakers
Alternatively buy 40 100uF metabolized polypropylene capacitors - with that quantity you should be able to get a discount :-)
Best of luck
Peter