I was looking for a small speaker without external power supply. He should be robust and be ready for immediate use on different computers. Decided I chose the Sonic Mobil 250. He fulfills all these characteristics perfectly. The only downside: For audio sources recorded softly I can not get enough volume from the speakers. Then I have to, really very rare, to switch to other speakers with similar price levels. However, these do not meet the claim small and robust.