Hee, hee. :lol: Good quality amps and speakers use direct-coupling with dual-polarity supplies or bridged amps and metalized-plastic film coupling caps for their very low distortion. :lol:Nigel Goodwin said:All you need to do for an electrolytic coupling capacitor (apart from ignore Audioguru's scare mongering [grin]) is ensure it has a DC potential across it the correct way.
There's also nothing particularly bad about speaker coupling capacitors, some of the most highly respected HiFi amplifiers in the world used them, and they still in great demand today!.
In an amp or in a speaker's crossover network, a cheap 6.8uF/100V electrolytic coupling cap costs pence, but a good film one costs a Euro. In addition to causing distortion, a cheap electrolytic cap has a wide tolerance that is unusable in a frequency-determining circuit, and its value reduces as it dries-up or leaks.
Even for my 6V Ultra-bright Chaser project I used two 1uF 5% film caps in parallel so they all spin at the same speed.
Electrolytic caps are fine in a power supply circuit. :lol: