A few factors you must know while shopping for a 4.1 Bluetooth Speaker. First, the Frequency Response - this indicates the range of the speaker. Wider the range louder is the audio output. Next, check the version of Bluetooth. This indicates the Bluetooth capability. Higher the number faster is the data shared between devices. Third, look for USB support. This means you can plug in a pen drive or even connect your mobile directly to the speaker to play audio. Additionally, if your mobile is running out of power, you can syphon off power from the speaker and charge your handheld device. Also, look for compatibility with other devices like your television, media player and laptop. Once you have identified the right brand and model, complete your purchase online at your preferred retailer, who offers you the best price.