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Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

RE: Has anyone tried "anti-parallel" capacitors in speaker crossover?

Note that your figure 6 shows the frequencies of MHz, not Hz.

This kind of neutralization of the capacitors series resonance will only affect the extreme upper range, well outside the audio band.

So while it might be of some benefit for AC power line filters in terms of RF suppression, it would have virtually no effect on an audio band speaker crossover behavior.

Note that the authors conveniently seem to overlook the result of placing a smaller value capacitor in parallel with the larger caps, one with smaller physical dimensions, and a much higher resonant frequency.

That is why power supply bypassing, and filtering situations often use more than one capacitor at a critical location, with staggered resonant frequencies via a range of cap values that cover a much wider range of low ESR resonant frequencies. A good rule of thumb for these situations is to use a cap value that is two decades smaller in value, with as many as three different sized caps in parallel, to provide a broad band region of lowered ESR at the RFI frequencies.

When there are large electrolytic's in use in a crossover, it is common practice to use a smaller value film cap as a bypass for the higher frequencies, mainly because the electrolytics have such a large amount of internal inductance.

Even the larger film caps, due to their physical size, can benefit from a smaller bypass film cap.

These smaller caps can then be of a higher grade than the larger film caps. Perhaps a set of polyester (mylar) larger caps, bypassed with a polypropylene or styrene cap.


Jon Risch


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