47 to 68 microfarads is good. That is usually around 800hz and will protect most tweeters from the frequencies that cause damage.yea cap. how do i choose which cap to use and at what uf?
Remember, it is there for protection, not to impact the actualy frequency response. So you want it less than your crossover, at least an octave.
Here is an actual calculator for it
Here is Andy talking about it.