There is a simple and easy way to tell which speaker is the left or right channel for sound. Below is a link to a video that plays audio specific to the left or right speaker:
If it is still hard to tell which speaker is left or right, please try putting any pair if 3.5 mm headphones into the output jack on the back of the BassPULSE. Since the headphones are labeled left and right, it will make it easier to tell.
Please contact customer service if the troubleshooting above does not solve the problem.