Bypassing Caps - what is it really about?

The 10uF film capacitors we use behave like near ideal capacitors almost to 1MHz. Bypassing that capacitor with a smaller one is not going to have any benefit.

I am not an electronics expert, but I know speakers well. For crossovers, this bypassing of a large capacitor with a small one, from what I have read, often very small, sounds like an urban myth that became real.

The effect of a capacitor in a crossover is related to its impedance at the frequencies you need it to work. Others have mentioned the capacitive element and inherent resistance and inductance. A 0.1uF capacitor is going to have lower inductance than a 10uF capacitor, but the resistance may be high, and at the same frequency, the effective of capacitance is 1/100. That 0.1uF capacitor is not going to fix any perceived issue with the 10uF capacitor. Maybe a 1uF and a 10uF, but then you have a much different capacitor and perhaps a 10% change in crossover frequency. Maybe if you are using first order crossovers, bypassing an electrolytic with a film capacitor if the film capacitor is a significant portion of the electrolytics values could be beneficial in a shunt location, by preventing frequencies at say 10x the crossover frequency. I am clutching at falling straws at this point.

Maybe in an amplifier or pre-amp bypassing an electrolytic audio coupling capacitor with a small film capacitor will have a benefit over the full frequency range, but I will leave that answer to the EEs.

See that’s your problem right there. You confuse $40 in parts and a weekend with experience. I have been designing speakers for professional applications for the better part of 2 decades. When you lack experience, you may be able to convince yourself with $40 in parts and a weekend that bypassing a capacitor that is ideal up to nearly a MHz provides some benefit other than just changing the total value. I don’t have such a luxury.

Pick a large respectable high end speaker manufacturer. Magico, B&W (high end), Wilson. Do they bypass their large capacitors with much smaller ones? No. Could they afford it? At those margins, of course, small capacitors are inexpensive. Why don’t they? It will have no benefit. Do you honestly believe these companies don’t know any better?

My comment is specifically about crossovers. I will leave power supplies to those that know better, and the same for capacitors passing audio signals in amplifiers and other electronics.

That’s your problem right there. Research without experience. $40 in parts and a weekend is worth more than all of the Internet.

@clustrocasual ,

If you means capacitors passing signals in electronics maybe there are some effects. In speakers though, you have to look at the combined effect of the capacitor and driver. If I bypass a 100uF (was mentioned above) electrolytic with a 1uF, there is no benefit because where the 1uF starts to provide any benefit, the driver has no output.

Oh come on. Do you think with million dollar development budgets that we never listened to anything?  What do you think companies who develop speakers do? Listening confirms measurements and measuring confirms listening. It is always a two way street.  Your "stroke your beard" comment is out of line. Just experiment sounds simple, but if you don't understand the basics, like how capacitors perform in a crossover, you are likely to make a flawed experiment and convince yourself of something incorrect. Then you will come on here and tell others about it like it was true.

There is lots still to learn. How to interpret the electrical characteristics of a capacitor and apply that to a crossover is not one of them. There are parameters of different capacitor constructions that some believe are audible. Dielectric absorption already mentioned and mechanical resonances being two, electrical resonance potentially being a 3rd influenced by ESR in the operating range a 4th. A small bypass capacitor will not solve any of those issues, nor make any change that is not swamped by component to component variation.

Do you really think these high end speaker companies have never thought of bypassing large capacitors with a much smaller one to make a better speaker?

When you lack an open mind you may be able to convince yourself your measurements and models are always adequate.

Takes an open mind and discerning ear to realize when one or the other has fallen short, and this topic is impossible to argue online.  That's why I make suggestions to audiogoners to experiment inexpensively and come to their own conclusions.  Or they can listen to you stroke your beard and tell us nothing is left to be learned.