Do I need a new Battery or Alternator for my car audio?

[Jack]

Right now i have a 1500 Watt amp and 2 12" Sub woofers (And new door speakers(don't know if that matters)) And when I have the music all the way up, each bass hit dims all the lights on my car. Now I want to add a 15" and another amp, but I'm not sure if it will be able to power it fully. What can I do to ensure everything receives maximum power? I heard something about needing a better alternator and a better battery, but I don't know. Thanks for any answers!

 

[Nomadd]

How is anybody supposed to know how good your battery and alternator is now?
Or how you hooked everything up? If you don't know how to find the problem with the voltage drop, there's very little chance you wired everything up right if you were the installer.
Your battery is a buffer and an old, worn out one could be a problem. Too small an alternator could be a problem. Grounding to the chassis instead of at the battery post or engine could be a problem, despite what so many "experts" say. You might need a big capacitor at the amp power input.
You might have a lousy engine to chassis ground.
There are a lot of factors in getting the system solid and it's not something you can learn in a Yahoo post.