The primary difference between a 2.1 and 3.1 soundbar that you should know of is that a 2.1 channel soundbar device features 2 distinct channels (left and right) along with an external subwoofer. These soundbars are often considered the baseline and are often the most economical and lower-end devices that you will come across in the market. On the other hand, a 3.1 soundbar has 3 distinct channels (center, right and left). These soundbars are a step up from the 2.1 models and include the center channel for better audio effects and dialogue.