A portable speaker, such as a subwoofer, that is configured to pair via Bluetooth from any device capable of streaming Bluetooth audio and act as the “sink.” The portable speaker is also configured to pair via Bluetooth to other audio equipment capable of streaming Bluetooth audio and act as the “source.” The portable speaker is also preferably configured to synchronize the audio signal going to the portable speaker and the other unit playing music, such that the user will not hear delays between the two units playing the audio stream. Preferably, the portable speaker is configured to be portable in which the size and weight is small enough for a person to carry, and is portable in which it operates with rechargeable batteries inside the unit, thus not needing any other power source such as AC outlet, or automobile power system. Another embodiment omits the speaker and instead provides a line out for connection to an external speaker, such as a subwoofer.