Vizio M-Series 5.1 (M51a-H6) – Review 2021

The Vizio M-Series 5.1 (M51a-H6) is more than just a soundbar. In addition to the bar itself, which has three distinct drivers, it combines with an included subwoofer and two rear satellites to deliver true surround sound for just $349.99. The system delivers impressive audio performance, and if that’s your main priority, it’s easy to overlook the less glamorous aspects of the design, such as the fact that the rear channels are wired to the subwoofer. Sure, you can increase your budget and get a more intense surround system, but for the price, this is an excellent setup for anyone seeking movie theater-like rumble, and earns our Editors’ Choice award for budget-friendly 5.1 soundbars.

A Functional Design

Available in black, the M-Series 5.1 soundbar measures roughly 2.2 by 36.0 by 3.7 inches (HWD) and can sit on flat surfaces or be mounted on the wall (brackets and template are included). Behind the grille, there are three 0.8-inch tweeters (left, center, and right) and three 1.7-by-3.5-inch full-range drivers (also left, center, and right). The entire system combines for a frequency range of 45Hz to 20kHz, and is DTS TruVolume, DTS Virtual:X, and Dolby Atmos compatible.

The soundbar’s back panel houses various connections, including HDMI in, HDMI out (eARC), an optical input, and a USB input (for streaming WAV/MP3 audio from thumb drives). There’s also a connection for the included power cable, as well as a 3.5mm input and a 3.5mm aux VA (for connecting to a voice assistant device like a smart speaker). So there’s no voice assistant functionality built in, but you can access one though the soundbar if you use the physical connection, which is bit of a quirky workaround.

An RCA-to-3.5mm cable is included, along with the cables for the surround speakers and the subwoofer. The inclusion of optical, HDMI, and aux input cables is generous for a system this price—often, even with expensive systems, you only get an HDMI cable.

The subwoofer measures approximately 10.0 by 8.3 by 11.7 inches and houses a single 6-inch down-firing driver. The two surround speakers measure roughly 2.0 by 6.0 by 3.5 inches and each house a 1.7-by-2.2-inch full-range driver. The cabling provided for each rear surround speaker, which terminates in mono RCA connectors on both ends, is generous in length; you will not likely need to unspool all of each cable. The speakers have rubber feet for tabletop placement, and they connect to the rear panel of the subwoofer. 

Setting the system up is easy. The soundbar automatically pairs with the sub and the connected surround speakers. Other than plugging the soundbar and the sub into power, the only thing you have to do is connect the soundbar to your audio sources with the included cables.

The remote control runs on two included AAA batteries and features a tiny display so you know what source and mode the bar is set to. There are also LED indicators on the left side of the soundbar’s front panel, behind the grille, that show you where bass, treble, and other paramters are set using 10 tiny LEDs, so you always have a visual marker.

Below the remote’s display, there are buttons for Input, Bluetooth pairing, Power, EQ, Level (for individual speaker channel and bass/treble adjustments), Setup (for adjusting various system parameters), and Effect (for cycling through, or disabling, the various effects settings). There’s also a mute button, plus/minus buttons for volume control, and a central OK button that handles playback, with forward or backward track navigation controls on either side. The backward track button can also be used to switch to the previously selected sound source, and both back/forward buttons are used to adjust and scroll through the various EQ and Effect settings.

Using the remote, you can adjust bass and treble levels, and make separate adjustments for dialogue levels, center channel levels, subwoofer levels, and surround speaker levels. You can also adjust the surround speaker balance for scenarios where one speaker might be closer to you than the other. Generally speaking, these are more detailed controls and audio adjustments than are included with plenty of soundbars we test.

Powerful 5.1 Audio

In addition to the aforementioned audio adjustments that can be made, the system has EQ modes you can select. Movie mode is the default setting, but you can switch to Music, Direct, and Game modes that are independent of the bass and treble controls, which we kept at mid-level settings for testing. For the films mentioned below, we stayed in Movie mode.

Blade Runner 2049’s crash scene, in which Ryan Gosling falls from the sky in something that looks like a military-grade Lamborghini that flies, features multiple explosions that pack some serious rumble through the M-Series 5.1. The film score alone sounds majestic and thunderous through the system, which does an excellent job of getting the right amount of rumble and thunder out of the sub in its default setting—it’s a theater-like experience out of the box.

The power and thunder this system brings to explosions, gunshots, and punches is impressive—it’s hard to sound this powerful at this price, and often, the sub-bass can sound unrefined, tubby, and muddled through other speakers. But here the sub packs some serious thump for its size while managing to retain definition, and the rear speakers really add a wonderful dimension. Getting them perfectly placed is important, but don’t forget you can also use the Levels parameters to adjust the individual channels if one speaker’s placement (or surroundings) makes it seem mismatched with the other.

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When the Death Star explodes in Stars Wars Episode IV: A New Hope, the system delivers the powerful explosion followed by a wave of sound you can feel moving past you to the rear surrounds. The dialogue is crisp, and when large ships fly overhead, the rumble is impressive. The rear speakers can struggle with it, but the trick is to dial the bass back a little (you can also dial the surround volume back if necessary). You can still keep the sub levels at the default setting, or even turn it up if you really want extra rumble that doesn’t get routed to the rear channels, as the sub doesn’t distort.

With the system switched to Music mode, it delivers powerful low-frequency depth on tracks with intense sub-bass content, like The Knife’s “Silent Shout.” Unfortunately, there’s some distortion in play at high volume levels. You’ll need to dial the bass levels down significantly to avoid it—the distortion seems to be in the midrange drivers of the soundbar itself, not the sub. At moderate volumes, there’s no distortion, and the system sounds powerful, with deeps lows and crisp highs. Even with the bass levels dialed back all the way, the M-Series 5.1 provides tremendous sub-bass thump, and the distortion disappears.

Bill Callahan’s “Drover,” a track with far less deep bass in the mix, gives us a better sense of the general sound signature. The drums on this track sound heavy, round, and powerful—there’s no distortion here. Callahan’s baritone vocals are delivered with an extra dose of low-mid richness and enough high-mid presence to maintain a crisp treble edge. We might prefer a slightly more crisp, brighter sound signature, but this is easily attainable by adjusting the default bass/treble settings.

On Jay-Z and Kanye West’s “No Church in the Wild,” the drum loop gets enough high-mid presence for its attack to retain its punchiness, while the sub-bass synth hits that punctuate the beat are delivered with less subwoofer power than we expected. So when you see that the frequency range begins at 40Hz, that means the sub isn’t reaching all the way down to 20Hz or below with all of its might, and that’s where the ominous rumble of these sub-bass synth hits lives. For the most part, the system provides more subwoofer power than we have any right to expect for the price, but the very deepest of lows are dialed back notably. The vocals on this track are delivered cleanly and clearly, with no added sibilance.

Orchestral tracks, like the opening scene in John Adams’ The Gospel According to the Other Mary, are delivered with a wonderful balance of crisp, bright high-frequency detail and slightly boosted low-frequency presence. If there’s something missing here, it would be a little more midrange, and that’s something you can’t adjust with simple bass or treble settings. For the most part, however, the M-Series 5.1 delivers a balanced, rich, and bright sound signature.

Affordable Surround

The Vizio M-Series 5.1 (M51a-H6) isn’t flawless, but if you put in some relatively simple work tweaking the sound signature with the remote, you can get to a place where there’s wonderful balance without distortion, and the rumble of the system doesn’t suffer for it. The sub delivers impressive, theater-like thunder, and music sounds powerful in the lows and detailed in the highs. For a little bit more money, we’re fans of the $400 Klipsch Cinema 600, while for less, the $200 Sony HT-S350 delivers solid audio for the price, though neither offers surround sound. If you have (a lot) more room in your budget, the $900 JBL Bar 9.1 delivers a wireless surround experience with speakers that charge by connecting to either end of the soundbar itself. But for $350, the M-Series 5.1 delivers rumble and granular audio controls that we weren’t expecting at this price, earning it our Editors’ Choice award.