The JBL Bar 2.1 has a 6.5" subwoofer, whereas the Bar 3.1 has a 10" subwoofer. The Bar 3.1 has two additional HDMI inputs, support 4K, and has a dedicated tweeter and two woofers to function as the center channel. These added features makes the JBL Bar 3.1 more efficient at producing bass, connecting multiple sources, playing Ultra HD content, and listening to voice/vocals.