If you like to watch movies or play video games, chances are that you've heard about surround sound. But what does it mean? Ultimately, surround sound uses multiple audio channels to create a more realistic and immersive representation of sound. Thanks to additional channel speakers, surround sound helps immerse you in your audio from all angles, allowing you to accurately place and localize objects like voices and sound effects to pinpoint locations within the soundstage. As a result, you feel like the action from your favorite movies and video games is taking place all around you. If you don't have space for dedicated speakers, there are also some options available that use speakers built into the bar, either with a phantom localization or by downmixing the content into stereo. While these options save space, they don't provide the same immersive sound.
To evaluate a soundbar's surround 5.1 performance, we perform several different tests, including localization, slope, standard error, 7.1 rears, SPL @ Max Volume, and weighted total harmonic distortion at 80 dB SPL and max volume.
Only certain types of audio content are mixed in a way that lets you take full advantage of surround sound technology. Common surround sound formats include Dolby Digital and DTS, which you've probably seen on streaming platforms and Blu-ray discs before. If you listen to a lot of stereo content - think most music and TV shows - you won't need to worry about how your bar performs with surround sound.
Close your eyes. Imagine you're sitting in the middle of a scene from your favorite movie. Let's imagine that there's a car chase. You can hear cars racing past your vehicle. The driver shouts at another character who's in the backseat of the car. Maybe there's gunfire. Maybe there's a helicopter flying overhead.
Think about where all of those sounds seem to come from. Each location is a little bit different, right? The other cars fly past you from your left or your right. The gunshot lands in an exact location. The character in the backseat of the car talks from behind you. The helicopter flies above your head.
Ultimately, a soundbar with a good surround sound performance can replicate this experience. It makes you feel as though you've been dropped right into the middle of the scene. That's because the bar can localize each of those different sounds - also called sound objects - to exact locations within the soundstage. It doesn't seem like sound is just coming from speakers placed in front of you - instead, it seems like the sound matches the action on the screen.
To test a soundbar's surrounds performance, we ensure that it only has a signal on its fourth and fifth channels. Then, we measure its frequency response using a microphone array and plot the results on a frequency response graph. Using this, we can determine its slope and standard error. We also record how loud it gets and its total harmonic distortion at a normal listening volume of 80dB and its max volume. These measurements can help show how clean and pure audio reproduction is and whether the soundbar reproduces audio the way it's meant to be heard by the engineer who mixed it.
We perform our surround channel tests with a similar setup to our stereo channel tests. We use a room that's 20' (L) x 16' (W) x 10' (H), with one couch and minimal sound treatment to represent a typical living room. We test with the soundbar placed 6.5 feet, 7.5 feet, and 8.5 feet away from the microphone array to get a better understanding of the sound profile at different positions. We use a laser measuring tool to ensure that the microphone array, table, and soundbar are at the appropriate distance from the side walls, and the subwoofer and the satellites if they're included in the setup. We test the surround channels using the same preset selected for our stereo frequency response tests and not with preliminary calibration. In some cases, we need to change the preset to get the surround channels to work, but we specify that in the text when it happens.
While many soundbars support surround content, not all of them reproduce that content in the same way. Localization describes how the soundbar is setup to playback surround content. Depending on the localization, the soundbar may offer a more immersive listening experience, and it may be able to more accurately localize objects like voices within the soundstage.
Ideally, your soundbar comes with dedicated or discrete surround channels - this is a "true" surround setup, and it provides the most realistic representation of sound. Other soundbars on the market use a "phantom" surround sound, in which side-firing speakers on the bar bounce sound off the walls to mimic the effect of dedicated surround speakers. However, in practice, phantom setups don't sound as clear or real as a discrete setup, and surround objects won't be as accurately localized within the sound image.
It's also possible that your soundbar has to downmix surround files into stereo to play it. Naturally, the result isn't as impressive as what you get with a discrete setup. With only the left and right stereo channels available, the bar plays content intended for both the left surround and left stereo from the left stereo channel. The same phenomenon occurs with the right channels. With more content forced into fewer speakers, the bar can't mimic an accurate placement of surround objects in the soundstage. For example, on screen, you'll see a car racing past from your left. In actuality, though, the sound just seems like it's coming from a speaker placed in front of you.
When looking for a soundbar, you're more likely to come across a 5.1 setup. However, some soundbars come with two additional rear speakers designed to support 7.1 content. A 7.1 configuration helps create a more immersive listening experience through the addition of two more surround channels, which can add more depth to your sound. It's especially useful if you have a larger living room and you're looking for a soundbar that can fill the entire space with sound without any holes in the soundstage. Some content's designed for 7.1 configurations, and while they're rare, they include certain video games and movies on streaming services.
That said, a 7.1 setup isn't necessarily better than a 5.1 setup. In a smaller living room, adding extra speakers can overwhelm the front channels with the audio that's mixed onto the surround channels. As a result, some effects seem louder than others, and you struggle to hear dialogue clearly. Ultimately, the best choice for you depends on the unique characteristics of your living space.
As part of our surround 5.1 tests, we measure the frequency response of the surround channels. With the bar calibrated at 80 dB, we play a sine wave tone between 20 Hz and 20 kHz and plot its output, in dB, on a frequency response graph. From the graph, we can see how accurately the soundbar reproduces the wide range of frequencies found in audio content, from the low-bass to the high-treble.
Ultimately, the slope of the frequency response graph shows the overall tonal balance of the soundbar's sound profile. A negative slope means that the bar reproduces more bass than treble, so it sounds thumpy, punchy, and boomy. A positive slope means that there's more treble than bass, which results in a sound that's bright, sparkling, or even piercing. A slope closer to zero represents a balanced sound overall.
As with our stereo frequency response tests, we don't score the slope of the surround channels' frequency response. Your personal preferences shape which tonal balance is ideal for you. For example, a balanced sound is suitable for most audio content, while a bass-heavy sound adds more thump and punch to help you feel the rumble in bass-heavy music and action-packed movie scenes.
Standard error is a measurement that shows the average deviation of the soundbar's in-room frequency response from the in-room target response. It can help you see how accurately the soundbar can reproduce audio at different frequencies, from the low bass to the high treble. Most surround content contains a wide range of frequencies, from the thumpy bass in action-packed scenes to the dialogue in the mid-range to the higher-pitched voices in the treble range.
For our tests, we use the Harman in-room response curve as our target. The Harman curve is the result of research that found the frequency response that sounds the most pleasing to most listeners, and it adds a little extra emphasis in the bass and a little less emphasis in the treble. It's ideal to find a soundbar with a low amount of standard error since this tends to represent a cleaner, more even sound that's closer to the target curve.
Usually, you can see which soundbars have a higher amount of standard error just by looking at the graph. If the frequency response fluctuates a lot, it probably has a higher standard error. If it's mostly flat and close to the middle, it probably has a lower amount of standard error.
Also, these fluctuations in the graph can give you a better idea of how the soundbar reproduces audio content at each frequency. For example, deviations in the bass range determine the amount of thump and punch reproduced by the soundbar, important for feeling the deep rumble in action-packed scenes. Voices reproduce in the mid-range, so fluctuations here make them sound muddy or push them to the back of the mix. Higher frequencies like S and T sounds reproduce in the treble range, so deviations here make them sound either piercing or dull.
Love to crank up the volume? This test is for you. It measures the soundbar's Sound Pressure Level @ Max Volume in decibels (dB) using a microphone array. Essentially, this measurement shows how loud the soundbar can get when you push it to its maximum volume.
In a traditional living room, a volume of 80 dB is more than enough to fill the room with sound. However, some bars get louder than that, and they're ideal for filling up large spaces with sound.
We consider a good value to be above 92 dB SPL since this gives you a lot of flexibility in selecting the volume for your audio content. While most of the bars we've tested score between 80 and 100 dB SPL, some can get even louder on their surround channels, like the Samsung HW-Q90R, which reaches 123 dB SPL on its surround channels.
Total harmonic distortion, or THD, is a measurement that shows the number of unwanted frequencies that the soundbar reproduces alongside the intended frequencies. Essentially, it compares the audio input (the video game or movie you're listening to) with the soundbar's output to see if the audio reproduces the way it was intended by whoever mixed it.
We calibrate the soundbar to 80 dB SPL using an SPL meter, which is considered a "normal" listening volume. Basically, a soundbar set to 80 dB gets loud enough to fill an average living room space with sound.
Then, we apply a spectrally pure sine wave and use the microphone array to measure the output. By comparing the input to the output, we can determine the amount of distortion produced by the soundbar. Our results add more weight to higher frequencies since you're more likely to perceive distortion at those frequencies. THD is difficult to hear with real-life content, so it's really only important for listeners who care about the fidelity of audio reproduction.
While 80 dB is considered a "normal" listening volume, it isn't suitable for everyone. For example, if you want to fill up a really large space with sound, you'll want a bar that lets you crank up the volume.
However, as volume increases, the amount of total harmonic distortion, or THD, tends to increase. This test is designed to see if the soundbar maintains clean and pure audio reproduction when the bar is pushed to its maximum volume. We measure the amount of THD on the surround channels at max volume. Again, we apply a spectrally pure sine wave and compare the soundbar's output with the input to determine the amount of distortion.
If you like feeling immersed in movies and video games, you'll want a soundbar with a good surrounds performance. Our tests evaluate the soundbar's soundstage and whether or not it can accurately localize objects within it. We also look at how accurately the soundbar can reproduce a deep bass and clear dialogue on its surround channels, how loud they get, and whether your audio reproduces without a lot of distortion. Ultimately, a good surrounds performance can help you feel immersed in your audio content from all angles.