It depends on how you wire up your subs and what ohm load is trying to be driven.
Gain will allow more of less voltage to the amplifier. sometimes to much gain or a over driven amp will begin to clip on signal wavelengths.
Personally, I don't think I would suggest that you crank your gain and bass boost.
that's just reckless.. and I never suggest having sub volumes cranked either.. besides
when you crank on things like your gain or bass boosts .. you'll only get more distortion.
I'm not saying this is always true, but its' very likely.
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side note - when you ask some how much bass boost to use and they laugh...it could mean their subs and amps are animals and do not require bass boost.
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Stopping the dimming in your lights....
This is going to happen .. but it does not have to happen . to help settle this issue you " could "
upgrade you alternator to something larger, and you could also find a larger battery and a lot of people do. If someone tries telling you that a cap will stop your lights from dimming.. thats not always true at all. I never got into them but they are more for those who have 90 million watt subs and 100 million watt amps... Im being drastic of course... are you paying attention ?
Some people with massive amounts of speakers and amps run SEVERAL alts and 15 or 16 batteries.