500uF 100V Non-Polarized Capacitor

I am trying to integrate a subwoofer into my full range system. While not absolutely necessary, a high pass crossover for the full range system is technically correct. A non-polarized 500 MF capacitors connected in series with each main speaker made a nice, cheap 40 Hz crossover.

I wonder whom manufactures these?

For those who don't know these non-polarized electrolytics (NPE's) are actually far superior to standard polarized power supply capacitors though they are considerably larger.

I would not have thought so but when someone said my measurents looked too good to be true I performed a series of measurements on standard electrolytics and NPE's and was suprised by the result.

I measured two samples of the 500uf value when they arrived and averaged the measurements.

Then I modelled a series RLC circuit and optimized the values to curve-fit the RLC model to the measured capacitor data.

The results were 514uf, 36mohm and 60nh with the impedance minimum at 29khz.