In my mind, there are two distinct types of soundbar. The first aspires to re-create a high-quality home theater experience in more convenient form factor. Whether it's a passive L/C/R soundbar like GoldenEar's SuperCinema 3D Array or a powered multichannel model like Focal's Dimension, these soundbars are usually more substantial in both size and price. The second is the entry-level soundbar sold at your local big-box retailer. This type of soundbar has much more modest aspirations: be better than the crappy speakers in a flat-panel TV, and take up as little space as possible while doing so.

VIZIO's new $500 SB4551-D5 soundbar system falls in the latter category. As the top model in the company's new Slim Series, it puts a high priority on keeping a low profile. The powered three-channel L/C/R soundbar measures just two inches high by two inches deep, with a length of 45 inches (it's designed to be mated with TVs that are 47 inches or larger). It comes with a wireless eight-inch subwoofer that measures just three inches deep, so you can hide it back against a wall or even lay it flat and slide it under your sofa.

This is a true 5.1-channel soundbar system, as it comes with two dedicated surround speakers that measure a little less than 2.5 inches wide by 2.5 deep by 5.5 high. The surrounds are powered by the amp inside the sub, which means you have to connect them to the sub using the supplied speaker cables. Thankfully, VIZIO provides very long cables, which gives you some placement flexibility for both the surrounds and subwoofer. The SB4551 comes with an IR remote that arranges its 11 buttons (power, source, menu, volume, mute, etc.) into an intuitive fashion and includes a single-line LCD through which you can adjust various functions.

The SB4551-D5 has excellent connectivity. Divided between two recessed panels on the soundbar's backside, you'll find one auxiliary analog input, one coaxial digital input, and one optical digital input to the right and one USB port and one HDMI 1.4 input to the left. There's also one HDMI output to pass through the video signal to your TV, and it supports Audio Return Channel to receive audio back from the TV's internal sources, like Netflix, over-the-air HDTV, etc.

The SB4551 supports wireless audio sources through Bluetooth and network audio streaming. The back panel has an Ethernet port, and the bar has 802.11ac Wi-Fi. Many of VIZIO's 2016 soundbars are SmartCast-enabled, meaning that they can be controlled through the company's SmartCast app for iOS and Android. Beyond just offering control capabilities, the SmartCast app allows you to link multiple SmartCast audio devices (including VIZIO soundbars and tabletop speakers) together for multi-room audio listening, and you can stream audio content like iHeartRadio from directly within the app to the soundbar.

Oh, and if all that's not enough, the SB4551 supports Google Cast. So, from any iOS/Android mobile device or from the Chrome browser, you can wirelessly transmit audio directly from any popular app that supports Google Cast--like Pandora, Spotify, Google Play, iHeartRadio, AOL Music, TuneIn Radio, and Plex.

So yeah, it's fair to characterize the SB4551 as "features-laden" for a sub-$500 soundbar. I tested a little bit of everything, connecting my Oppo BDP-103 Blu-ray player via HDMI, a Hopper DVR via optical digital, Bluetooth streaming from my iPhone 6 and Macbook Pro, plus a little Google Casting from Pandora. I connected the SB4551's ARC-enabled HDMI output to an LG smart TV and had no issues receiving audio back from LG's internal Netflix app.

Through either the remote control or the SmartCast app, you can adjust a lot of audio parameters on the fly. Bass and treble adjustments are available, as are level adjustments for the center, surrounds, and subwoofer. There's even a Speaker Level tool that plays audio tones to help match levels between all the speakers and sub, if you have an SPL meter. You can enable or disable the Surround mode and turn on DTS TruVolume to reduce volume discrepancies between sources. It's a lot more intuitive to make these adjustments within the SmartCast app, where you can see all of them on a big screen at once...but the remote control gets the job done, too.

Now let's talk audio performance. First, what the SB4551 does well. On its website, VIZIO touts two main performance parameters: dynamic ability and bass output. VIZIO claims the system can play up to 104 dB. I did not test that claim, but I will confirm that the system has excellent dynamics that surpass expectation for speakers this small. Whether I used it in my enclosed family room or my large, wide-open living room, with movies or music, the SB4551 filled the room with sound.

It also filled the room with respectably deep bass for an eight-inch woofer. Many soundbar systems in this price range use a seven- or even a 6.5-inch woofer. In everybody's favorite subwoofer demo test, the depth-charge sequence in U-571, I did hear some of the deeper rumbles. They weren't super-loud or room-shaking the way you'll get with a good 12- or 15-inch sub, but there was solid low-end presence. Likewise in scenes from Ironman and The Matrix. I tried the sub in a variety of locations, both in back and front of the room near the wall, as well as under my couch. I felt that the under-the-couch placement drew too much attention to itself; but, if you like the whole "tactile transducer" thing, then you might enjoy that placement. Ultimately, I preferred the sub up front, closer to the soundbar, to get the most cohesive presentation.

Another positive trait is vocal clarity, which is arguably the most important trait in these lower-priced soundbars meant to replace TV speakers. The SB4551's dedicated center channel produces clean, intelligible dialogue with both male and female voices, and the ability to adjust the center-channel level on the fly is a nice perk. For the most part, the various high-frequency effects in action movies sounded crisp and precise without being overly harsh or tinny.

Where does the SB4551 struggle? Well, its driver and cabinet size should give you a hint. We're talking about a soundbar and two surround speakers that all use two- by- four-inch full-range drivers in a two-inch-deep cabinet, so they can only play so deep and handle so much. There's just not much meat in the lower midrange, and the soundbar struggles to reproduce all of the complex, bombastic effects in dense action-movie sequences. In scenes from The Matrix and Ironman, I could barely hear a lot of music and background effects that I know should be more prominent, and the soundbar itself sounded compressed during big explosions.

In a lot of these miniaturized systems, the crossover is set quite high to let the sub handle that lower midrange info; but then, you run into issues where you're asking a sub to handle vocals and other specific effects that it wasn't meant to handle. No one wants to hear voices coming from a sub, especially if you put the sub in the back of the room. I count it as a plus that I did not hear any vocals coming from the SB4551 sub, so I'm guessing VIZIO chose a lower crossover point (the company doesn't list the crossover frequency) - but the result is the speakers are asked to go lower than they are really able to do.

Obviously, music reproduction is not a soundbar's first priority, and when I fed the SB4551 my usual assortment of AIFF test tunes an in official evaluation capacity, it was easy to hear the shortcomings: a lack of openness and air in the highs, a lack of meat in the mids, and bass notes that weren't particularly distinct or defined. But let me add this: when I moved away from critical listening and just casually streamed compressed music over Bluetooth or Wi-Fi, I found the SB4551's performance to be perfectly acceptable. The good dynamics, clean highs, and solid bass worked well together for casual everyday music streaming, which is exactly how this soundbar is likely to be used. And you can't discount the convenience of being able to stream music to the SB4551 from just about any source.

High Points
• The SB4551 offers good dynamic ability, vocal clarity, and bass response.
• The system has a very low-profile form factor, with a flat sub that is easily hidden.
• The SB4551 offers a lot of connection options, including HDMI pass-through and ARC to receive audio from your internal TV sources--which is rare at this price point.
• The inclusion of Bluetooth, SmartCast, and Google Cast gives you plenty of wireless streaming options.

Low Points
• The system sounds lean in the mids and can't reproduce all the complex details in the densest action-movie scenes.
• The USB port only supports WAV file playback, which seems like an odd choice.
• The surround speakers need to be wired to the sub, which means you may still need to run speaker wire around your room if you want to put the sub closer to the soundbar (where it sounded the best, in my case). All in all, the surrounds are so tiny and contribute so little to the overall experience that you might be better off saving yourself $50 and getting the 3.1-channel SB4531 system that omits them.
• Because the inputs are divided between two connection panels on each end of the soundbar, it's a bit more challenging to route the cords. Plus, the soundbar is so light, it's easy to accidentally pull it over or off its stand if you don't secure away the cables away carefully.

Comparison & Competition
Although $500 is certainly a lower price than the dedicated home theater-oriented soundbar systems we often review, it still falls at the high end of the "entry-level" category. There are obviously a ton of soundbar/subwoofer options priced under or around $500 from the likes of Bose, Yamaha, Polk, Zvox, Samsung, LG, and more. However, a lot of these options are two-channel soundbars that lack the dedicated center channel and the separate surround speakers that you get with the VIZIO SB4551. Most of them have Bluetooth but lack HDMI inputs and video pass-through.

Yamaha's $500 YSP-1600 is a 5.1-channel soundbar, but all five channels are housed in the soundbar, and the bar utilizes Yamaha's Digital Sound Projector technology to simulate a surround soundfield. The $500 ZVOX SoundBar SB400 is a three-channel soundbar with three two-inch drivers and a four-inch woofer. Polk offers the $500 MagniFi 3.1-channel soundbar, or you can step up to the $700 Omni SB1 Plus 3.1-channel system with DTS Play-Fi technology. You can add wireless surrounds via Play-Fi, but you have to buy them separately.

Another option worth considering at this price point is a pair of powered bookshelf speakers or a 2.1-channel desktop system from the likes of Klipsch, Polk, or Audioengine. $500 can buy a good pair of powered speakers with digital inputs and Bluetooth, plus larger drivers that can put a little more meat on the bones.

Conclusion
Like many VIZIO products, the SB4551 5.1-channel soundbar system is a strong value in the category, offering a lot of features--like HDMI pass-through, dedicated surround speakers, and Google Cast support--that you don't find in many soundbars at this price. Its overall performance is solid but not earth-shattering. It's a fine choice for a more casual environment like a bedroom or den--someplace where you want better, bigger sound than your TV speakers can deliver, as well as the convenience of wireless audio streaming, in one small, easy-to-control package.

Additional Resources
• Check out our Soundbars category page to read similar reviews.
• VIZIO Introduces Crave Series of Tabletop Speakers at HomeTheaterReview.com.
• VIZIO Acquired by China-Based LeEco for $2 Billion at HomeTheaterReview.com.