I have a few questions from Danny's recent servo sub video, regarding the high pass filter section.

Can you do a high pass filter on an XLR cable, and if so would that mean two capacitors in the filter? One for the normal signal and the other for the reversed signal? I assume both caps would have the same value.

And then for determining the crossover point for the filter. I assume you want to measure where your mains are 3db down in room and target that figure?

Regarding determining the amplifiers input impedance. Would you just go from the data sheet specifications from the manufacture? Or do, or can, you measure this?

Now after you have a good crossover point determined and know the input impedance of the amp, you just plug those value into a high pass filter crossover calculator and get your capacitor value. If your calculated value falls in between two values of readily available capacitor, you go to the next highest one right? Put differently if my calculated values is 0.33uf but I only can find a 0.30uf or 0.36uf capacitor, I'd go with the 0.36uf cap right?

Thanks in advance for any advice.