Also the problem with caps in a car audio system is that when they draw down, the overall load on the system goes up considerably. They reduce flickering, sure, but the overall performance of the electrical system doesn't change much unless you have a rather large cap bank to supply the demanded loads without dropping voltage too much.
1-10 farads isn't going to cut it if you think about how the farad rating works vs what the sound system's burst draw is capable of pulling.
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