Portable speaker device used for portable multimedia device

A portable speaker device used in a portable multimedia device is provided to improve sound quality of an audio signal by outputting the audio signal through a speaker adopting a high performance/high output digital amplifier. In a portable speaker device(200) used in a portable multimedia device(100), a 2 channel virtualizer receives a digital audio signal from the portable multimedia device and provides sound field effect to the received digital audio signal. A digital amplifier performs digital processing of the digital audio signal outputted from the 2 channel virtualizer and then outputs the digital audio signal to a speaker. A battery provides a power supply voltage to at least one of the digital amplifier and the portable multimedia device.