Your pulling more power then your alternator can produce so it tries to pull more. That's why people with big setups have to rev the engine or set up separate batteries. Sent from AutoGuide.com App
Exactly what it is. Had it happen in my old explorer when I had a pretty large setup. Best bet is to set up a battery in the trunk to power the subs, so you're not pulling all the power from the rest of the car.