passive crossover help Please

Hi, I currently am using a Magnaplanar X0-1 box as a highpass filter for my Acoustat electrostics. I am using a .0206 Wondercap cap. This is supposed to give an approximately 85 hz cutoff. I was using an AudioPro B2-50 sub with a variable crossover set at around 85-90hz. Well I got a new MBL sub and it only has 70 and 100hz. What size cap should I get to change the crossover to around 70hz? Bigger I guess? What exact size would you guys recommend? I haven't messed with this stuff in 15 years and don't remember all the formulas. My Muse 160 has an input impedence of 10K ohms. The XO-1 box is wired internally with one wire going from the input+ to a volume control(1 for each side), another wire going from the volume control to sub out+ and the cap is wired to the subout+ and the high out+. Everything is grounded together. This works and sounds fine with Audiopro but the MBL doesn't. I want to cross the Acoustats over at around 70. Any help or suggestions would be greatly appreciated. Thanks
Post your question at discussion section. You will get help there. Make sure you title the subject please.. or somthing like that.
The formula for calculating the size of the capacitor is: c=1/(2*pi*r*f) So, for a 70hz cutoff with a 10K input inpedence the result is: c = 1/(2 * 3.14159 * 10,000 * 70) c = 0.227uf For best results use a Hovland Musicap.