The "polite" breakdown of this thread:
1) Being loud outside of the vehicle should be the least of your concerns. It is actually a good thing that you like how it sounds inside the vehicle, and it isn't very loud outside the vehicle.
2) Don't listen to your brother ever again. The sub is unimportant when it comes to volume outside of the vehicle. Sub placement (in the vehicle) and the vehicle itself are, however.
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