As you can see, you do have several options with these speakers. One of the best features is being able to choose the power source. Most external speakers require you to use an AC adapter, but with these, you can plug them directly into your laptop for power. This makes the speakers completely portable. If you don't want to use these with your laptop or have limited USB ports, you can use batteries (rated to give about 30 hours) or buy an AC adapter..



Link: Notebook Review