From Dolby Digital and DTS movies to video games, there are many types of multi-channel content that you'll want to listen to using your soundbar. A good surround performance can help to immerse you in your audio from all angles, allowing you to accurately place and localize objects like voices and sound effects within the sound image. Otherwise, surround sound may seem like it's coming from a speaker placed in front of you, which can be disappointing for many listeners.
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.
If you like to listen to multi-channel content like movies and video games, you'll want a soundbar with an immersive surround performance. When listening to surround content, you'll want to feel like your audio is coming from all around you and that objects in the sound image like voices and footsteps are accurately localized. It's also important that the soundbar can reproduce a deep, thumpy low-bass and make voices and instruments sound clear. Also, you may want to crank up the volume on your surround channels without experiencing a lot of distortion. However, if you mostly listen to stereo content like music, you may not be interested in a soundbar's surround performance.
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 your audio reproduction is and whether your 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 18' (L) x 16' (W) x 9' (H), with one couch and minimal sound treatment to represent a typical living room. The soundbar and the table it sits on are 7.5 feet away from our microphone array. We test with the soundbar placed 6.5 feet and 8.5 feet from the microphone 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.
Some soundbars come with dedicated or discrete surround channels. Others may use side-firing speakers to simulate surround objects in the soundstage. However, this phantom setup doesn'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 possible that the soundbar doesn't support surround content and has to downmix it into stereo to play it. This means your audio will seem like it's coming from the front rather than from speakers placed all around you.
While most multi-channel content is in 5.1, some movies and video games support a 7.1 speaker configuration. A 7.1 configuration helps to create a more immersive listening experience through the addition of two more surround channels.
Some soundbars come with two additional rear speakers designed to support 7.1 content. However, it's rare, and only a few of the soundbars we've tested offer 7.1 rears, including the Samsung HW-Q950T and the Nakamichi Shockwafe Ultra 9.2Ch. We don't test this, but instead, we look to see what the manufacturer reports.
As part of our surround 5.1 tests, we measure the frequency response of the surround channels. We play a sine wave tone at -6 dB FS 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 may sound thumpy, punchy, and boomy. A positive slope means that there's more treble than bass, which can result 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. Depending on your personal preferences, you may prefer a soundbar with a different tonal balance. For example, a balanced sound is considered suitable for most types of audio content, while a bass-heavy sound can add 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 and lead instruments in the mid-range to the cymbals and other 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 tends to fluctuate 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 and instruments reproduce in the mid-range, so fluctuations here can make them sound muddy or push them to the back of the mix. Higher frequencies like cymbals or S and T sounds reproduce in the treble range, so deviations here can make them sound either piercing or dull.
For many listeners, it's important to find a soundbar that can get loud so their audio content can fill up a large room or a crowded party. We measure 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.
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, such as the LG SN11RG, which reaches 125.7 dB SPL.
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 for most users. 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. For most people, THD can be difficult to hear with real-life content, so it may only be important for listeners who care about the fidelity of audio reproduction.
If you like to listen to your audio at loud volumes, you'll want 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 total harmonic distortion, or 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.
Most of the soundbars we've tested experience a slight jump in THD when pushed to their maximum volume. However, for most people, distortion can be difficult to hear with real-life content, especially if the weighted amount of THD remains below one.
If you like to listen to surround sound content, 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 the sound image. 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.