I am using Quantum USB Mini Speaker since 2 years and it is an efficient speaker in low price range. You can attach it with laptop and mobile phones and can enjoy high pitch volume. Although sound quality is good yet base of the sound is untraceable, which makes it a less ordinary speaker.
Due to its small size you can carry it anywhere but always take care of USB wire because a little stretch can do a problem.
I like this product because in less price you can not a find better speaker than this one. I am satisfied with this speaker.