So a while ago I found out about these things called "Boomcases" ( http://theboomcase.com/ )
But I didn't like the price and the appearance.
So I decided to build my own.
But I didn't want to spend to much money.
So I grabbed my JBL On Stage IIIp and took it apart to see if it worked with normal speakers.
It worked like a Charm!
I found out what the problem was.
The batteries had a total of 9 Volts, And at that level the bass will reduce to make it last longer.
So I took 2 battery holders (4 AA batteries per holder) and wired them up together.
The two of them together makes 12 volts.
This is only temp. since I'm going to buy better speakers.
This will work with every portable speaker system (as far as my knowledge goes).