Looking at the 31 and 21 Soundbars
I've spent the last three years testing budget and mid-range soundbars for people who just want their TV audio to not sound like a cardboard box. A lot of them end up standing in the same aisle staring at two similar-looking bars from the same brand and wondering which one to buy. The short version is that the differences are real but they don't always matter for your actual room. The 31 and the 21 are positioned one step apart in the lineup, and that gap shows up in a few specific areas. The 31 gets a wider driver array, usually with two additional passive radiators for bass response. The 21 sticks to a more compact enclosure with a simpler crossover network. Both run similar DSP profiles, so dialogue clarity is close. Where they diverge is in room-filling width and low-end extension below 60 hertz. I set both up in the same living room last winter. It was a 14 by 16 foot space with a leather sofa facing a 65 inch panel mounted on a drywall wall. No acoustic treatment. Just the furniture, a rug, and a window on one side. I ran the same calibration tone through each bar using the built-in room correction. The 31 placed the center channel image slightly wider across the front soundstage. The 21 kept the center anchor tighter but lost some of that spread. It was not a huge difference. Maybe a 10 to 15 percent gap in perceived width. But once you hear it, it is hard to unhear.
Here is the thing most people miss when comparing these two. The 31's extra bass radiators only help if your TV stand or wall mount allows proper airflow behind the bar. I learned this the hard way. My first install had the 31 pushed flush against a closed media console with no gap. Bass became muddy and the low frequencies collapsed around 55 hertz. I pulled it forward about two inches and added a foam baffle behind it. The mud cleared up almost immediately. The 21 does not have this problem because it simply does not try to produce as much low end. It is less flexible but also less sensitive to placement mistakes.
What matters for your actual setup
If you watch a lot of movies with heavy bass tracks and your soundbar sits on an open shelf or is wall-mounted with clearance, the 31 will give you a fuller experience. It handles action sequences better and the bass extension reaches lower before rolling off. Dialogue remains clear because the DSP keeps the midrange focused. If you are watching mostly TV shows and news with occasional movies, the 21 covers that well and it costs less. The savings are not trivial. You are looking at roughly a third of the price going from the 31 down to the 21. Both units support HDMI eARC and have optical input. Neither has Dolby Atmos height channels built in, so do not expect ceiling reflections or upward firing drivers. They are stereo bars with virtual surround processing. The processing on the 31 is slightly more aggressive and can feel immersive during wide scenes. The 21 is more restrained and sometimes sounds a bit flat during quiet dialogue passages. I found myself nudging the treble boost one step higher on the 21 to get speech to sit above the background mix. I also tested both with a wireless subwoofer added. The 31 pairs cleanly with its matching sub and the transition between main bar and sub is smooth around 80 hertz. The crossover point is fixed at that frequency. The 21 can pair with the same sub but the integration feels a touch rougher at the handoff. There is a small dip in output right around the crossover that becomes noticeable when you do a quick A-B switch. It is subtle but it is there.
Get the Full Details
Where neither bar succeeds
I need to be blunt about the limitations. If your room is larger than 18 by 20 feet, or if you have open floor plans that bleed into kitchen and dining areas, these bars will struggle. The output simply does not carry. Sound dissipates too quickly and you end up turning the volume up until neighbors complain. For those spaces you should look at a system with separate speakers or at least a soundbar with a dedicated rear cluster. Neither the 31 nor the 21 will fill that room properly no matter how you position them. Another issue is the remote. Both come with basic remotes that lack backlit buttons and have stiff keys. If you frequently adjust volume late at night, you will press the wrong button. I started using a universal remote for this reason. It saved me from accidentally muting the bar during a quiet scene three times in one week. HDMI handshake issues showed up on both units during my testing. I had a period where the 31 dropped ARC signal every time I switched from my cable box to a game console. The fix was to use an HDMI switcher with external power rather than relying on the TV's eARC port alone. The 21 did not have this problem in the same setup, which surprised me. YMMV depending on your TV and source components.
My recommendation
Pick the 31 if you have a medium sized room, want better bass without adding a sub, and can give the bar a little breathing room during install. Pick the 21 if you are on a tighter budget, mostly watch standard content, and want something that works reliably out of the box with minimal placement fuss. Both are solid choices for their respective spots. The gap between them is noticeable but not enormous. It comes down to how much space you have and what you actually watch.
