Help with crossover cap value

[flip]

I am in the process of hooking up my vandersteen stereo subs to my beloved paramours. I have a 20K in line crossover for my B&K amp which Vandersteen made up for me. I need to make some up that are 272K, I believe that is what the input impedance is for the paramours.
My 20K xover has a .01cap in parallel with a .08 cap. With my 5th grade math skills I can't figure this out. Any help would be great!

                                                                            Thanks

 

[Grainger49]

Flip,

I am having some trouble understanding.  The 20k in line crossover for your B & K amp, are you saying that it has an input impedance of 20k ohms?  Certainly not a high pass or low pass frequency of 20k Hz, right?

If the 0.01uF cap is in parallel with a 0.08uF, they add to 0.09uF.  But how are they wired?  That is, are these capacitors in series with the center lead, hot, wire going into a 20k ohm input impedance of the B & K?

I guess I am also asking what the in line crossover does for the B & K amp.

 

[flip]

Hi Grainger,

Thanks for replying, you have helped me out before with my FP.
The 20k crossovers are 2 caps, stacked on top of each other, ends twisted together. 1 lead goes to the Hot of a male rca and the other lead goes to the hot of the female rca jack. Then there is a ground wire run to the side of the male and female jack. Its wrapped in heavy shrink tube, male end goes in the input of the amp and then just connect your interconnect the female end and then to preamp out. It rolls the main speakers off at 80HZ and the the lows go to the subs.It works great with the B&K which has a input impedance of 24k. I am trying to get that seamless bass connect with the paramours, just don't know how to figure the cap values.

 

[Grainger49]

Ok, I got it now.  My Paramours have an input resistor of 270k ohms.  For an 80 Hz 3dB down frequency that calculates to a capacitor of 7,368pF.  That is 0.007368uF.

I calculated the Vandersteen crossover at 88.419 Hz for an even 20k ohm input on the B & K.

If your Paramours have 272k ohm resistors then the value calculates to 7,3141pF or 0.0073141uF.

This all assumes I can still work my old HP15C calculator.

 

[flip]

Thanks a bunch Grainger. Now I just have to find the caps. I'll let you know how it works out . Wish my brain could work like that..

                                                              Thanks ,Jim

 

[Grainger49]

You see how odd the capacitor design values calculate to be.  Also, you see that Vandersteen didn't use what they calculated either, the crossover is 88.4 Hz not 80 Hz.  Just use what is available close to the "Design" value.

I see 3000pF and 4700pF caps for sale.  Those in parallel will give you 7700pF.