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Vizio M-Series 5.1 M51a-H6 review

The affordable Vizio M-Series 5.1 M51a-H6 soundbar system delivers true surround sound, Dolby Atmos and a lot of bass

Vizio M-Series 5.1 M51a-H6 review
(Image: © Vizio)

Our Verdict

Vizio’s M-Series 5.1 M51a-H6 gives you a lot for the money, but you need to work to get it to sound its best.


  • True surround sound with Atmos support
  • Lots of audio and input options
  • Affordable


  • Bass lacks detail
  • Takes work to get the right sound
  • No upfiring speakers

Vizio’s M-Series 5.1 Home Theater with Dolby Atmos and DTS:X M51a-H6 is a soundbar system with a long name and an even longer list of features. The M51a-H6 features a subwoofer and satellite speakers, so you get true 5.1 surround sound; supports Dolby Atmos and DTS Virtual:X for the latest in immersive sound; and comes with many, many ways to adjust the audio you hear. Even so, its best feature may be the price: just $250 for the whole package.

But while this system challenges the very best soundbars on sheer value, it needed some significant experimentation with the options before it realized its potential. As our Vizio M-Series 5.1 M51a-H6 will explain, if you’re looking for a “set it and forget it” soundbar, this may not be the right one for you. 

Vizio M-Series 5.1 M51a-V6

The Vizio M-Series 5.1 M51a-V6 is one of the cheapest soundbar/subwoofer/satellite combos we’ve tested, at $250. This is down significantly on the $350 list price, but even that would be pretty good value considering how much you get.

You can pick up the M51a-V6 from CostCo or direct from Vizio.

Vizio M-Series 5.1 M51a-V6 review: Design

The M51a-H6 looks like it costs more than it does; it has an elegant design with rounded edges and a charcoal color that doesn’t attract too much attention.

Vizio M-Series 5.1 M51a-H6 review

(Image credit: Tom's Guide)

The 36 x 3.5 x 2 inch main soundbar features 6 drivers, all forward facing — unusually for an Atmos soundbar, there are no upfiring drivers on top for height.

Vizio M-Series 5.1 M51a-H6 review

(Image credit: Vizio)

The wireless subwoofer measures about 11.8 x 9 x 8.4 inches and has a 6-inch woofer inside. The sub includes wired outputs for the left and right satellites, each about 5.8 x 3.5 x 2.3 inches.

Vizio M-Series 5.1 M51a-H6 review

(Image credit: Vizio)

The top of the soundbar has power, input, Bluetooth pairing and volume controls, while LEDs on the front-left show you the volume level. Different combinations of the lights also flash when you change inputs or sound modes. A green light shows when Dolby Atmos is engaged. 

Vizio M-Series 5.1 M51a-H6 review

(Image credit: Vizio)

On the back you’ll find an HDMI Out to connect to your TV, as well as one HDMI In for external devices such as a streaming box or a game console. There’s also an optical digital audio input, USB input and two 3.5mm auxiliary inputs. One aux input is for connecting a TV and another, labeled Aux VA, for a voice assistant speaker — a feature shared with the similarly affordable Vizio V21-H8 soundbar.

Vizio M-Series 5.1 M51a-H6 review

(Image credit: Tom's Guide)

The Aux VA input stays active even when you switch to other inputs, allowing always-on access to your voice assistant. It’s a handy addition and clever way to make use of your existing voice-enabled speaker. 

The Vizio remote does a lot of heavy lifting, especially since there’s no app for the system. It has a small display at the top that shows options as you select them. For example, if you select Input, you can scroll through HDMI eARC, HDMI in, Bluetooth, and others.

Vizio M-Series 5.1 M51a-H6 review

(Image credit: Tom's Guide)

The speaker also says the input or sound mode selection when you change it. That’s a lot to ask of a little remote, but I found the screen easy to read and the options fairly intuitive to navigate. You may want to check the manual to see which options are under each menu. 

Vizio M-Series 5.1 M51a-V6 review: Performance

No matter how good virtual surround sound gets, it has yet to beat the real thing. Having satellite speakers on the M51a-H6 improves the immersive experience of watching a movie or playing a game. Dolby Atmos and DTS:X support makes the effect even more precise, too. When Thor throws his axe in Avengers: Infinity War, you can practically feel it move through space thanks to the surround speakers. It’s hard to fake that. However, the M51a-H6 lacks upfiring speakers, so you miss the height effect when Thor brings the lightning down. 

The M51a-H6 is a bass-forward soundbar, which can be great for a tactile listening experience. But depending on how you set up the speaker (see the Setup section below), the low end can completely overwhelm everything else. In 2004’s Man on Fire, when Denzel Washington started blowing up cars, the floor shook so much that my windows rattled. But the sound from the subwoofer lacked any definition — it was just a muddy roar. I was able to improve the effect by moving the subwoofer and lowering the level, but that didn’t change the detail coming out of the sub. 

Vizio M-Series 5.1 M51a-H6 review

(Image credit: Vizio)

When the subwoofer is under control, voices sound full and resonant. Lady Whistledown’s voiceovers in Bridgerton were easy to understand, as were the conversations between Malcolm X, Cassius Clay, Sam Cooke and Jim Brown in One Night in Miami. 

Music sounds full and bright, if you don’t mind listening to your music in surround sound. In Music mode, The Weeknd’s vocals on “Bright Lights” were full and warm while the bass resonated nicely; the acoustic guitar on Fleetwood Mac’s “Never Going Back Again” was sharp and realistic. But using Direct mode — which plays stereo instead of surround, as the music was recorded — the vocals and instruments were flat, with only the bass remaining impressive..

The M51a-V6 is one of the loudest soundbars I’ve tested, pushing over 100 decibels at full volume. The sound distorted at that level, but sounded relatively clean even at 90 decibels. You won’t have to worry about whether this system can fill your room. 

Vizio M-Series 5.1 M51a-V6 review: Setup

The M51a-V6 offers a couple of different ways to arrange the soundbar, satellites and subwoofer. Vizio’s recommended placement has the soundbar under the TV, the satellites behind you and the sub next to where you sit. This may be because you connect the satellites to the sub via wires, and this arrangement keeps the cables out of your way. You can also put the satellites in front with the soundbar, and put the sub next to the TV — if you do this, be sure to switch the satellite arrangement in the remote’s Setup menu. 

Vizio M-Series 5.1 M51a-H6 review

(Image credit: Vizio)

Having the sub next to me made the low end way too dominant in the sound mix, even if I turned the sub volume down. Having the satellites in front also eliminated the benefit of having rear speakers — the sound didn’t move around me. I settled on having the sub in front, near the TV, and placing the satellites behind me with the wires running across the room. This might not be Vizio’s recommendation, but to my ears it provided the best balance of bass and surround sound. The right arrangement for your room may vary; but at least you have plenty of options to make it sound as good as it can. 

I used an HDMI cable to connect the M51a-V6’s HDMI Out to my TV’s eARC HDMI port and was quickly listening. That connection allowed me to use my TV’s remote to control the volume. However, the M51a-H6 didn’t turn on when I powered on the TV — I had to use the Vizio remote. 

After finding the best placement of the speakers for your room, there are a ton of additional tweaks you can make to the audio. Equalizer options include Movie, Music, Direct and Game; you can also separately boost Dialog, Bass and Treble levels. You can also manually change the level of the Center, Subwoofer and Satellite channels. The Satellite level doesn’t differentiate between the right and left, but you can adjust the balance between the two. 

The Setup menu has even more settings to fiddle with, too. That’s a lot of potential ways to make the sound the way you like it, especially for an inexpensive soundbar. 

Vizio M-Series 5.1 M51a-V6 review: Verdict

The M51a-H6 delivers true 5.1 surround sound and it costs about the same as — or less than — soundbars that have to use virtual surround to try to achieve the effect. It has a lot of flexibility, whether that’s in the way you arrange the speakers, connection options or audio adjustments. And it sounds pretty good, too. 

But it takes effort to make it sound its best, and soundbars are supposed to be simple to use. In this price range, you’ll find some excellent soundbars that are easier to set up, such as the Yamaha YAS-209 or, for a little more, the Sonos Beam

But, neither of those come with satellite speakers, or offer Atmos support. If you’re looking for true 5.1 surround sound with Atmos and want to spend less than $400, the M51a-H6 is the one to buy.

Michael Gowan

Michael Gowan covers soundbars, TVs, portable speakers and other audio- and video-related topics for Tom’s Guide. He’s written about music and technology for more than 20 years for a raft of publications including Wired, Men’s Journal, PC World and Macworld. When he’s not reviewing speakers, he’s probably listening to one anyway. 

  • WeedWhackerDood
    An update needs to be provided by Uncle Tom to highlight that the Vizio M51a-H6 has a VERY HIGH rate of fatal failure and that Vizio is no longer providing warranty replacements, only refunds.

    Costco and Sams are still taking these defective bricks back as returns, but there is no guarantee this will continue. Costco is still selling this model, but consumers should stay away and buy a more reliable system.

    This product sounds wonderful, I absolutely love the sound, while it worked I should say. My failure rate on 2 of these systems was <6 months, other consumers have had failures between 1 -6 months and that is disappointing.