How are you connecting your music source to the speaker. If it's a cable from a phone headphone output to an single XLR or TRS input on the speaker that is your problem, you can't inject an unbalanced stereo signal into a single balanced mono input because everything common on booth channels(usually all the low frequencies) gets cancelled.
The correct cable to use in this case is a 1/8" TRS to dual 1/4" TS.