When looking for a soundbar, you'll want a product that can reproduce the wide range of frequencies found in music, movies, and TV shows. Using a frequency response graph, we can see how much sound the bar can reproduce at each frequency, allowing us to better understand a soundbar's sound profile. A neutral sound profile is considered versatile enough for listening to lots of different types of audio content, but your preferences may vary depending on personal tastes and the type of audio content you like. For example, a bass-heavy sound profile can add extra thump and punch to bass-heavy music genres and action-packed movie scenes, while a v-shaped sound can add excitement and brightness to your audio.
We test for a couple of factors that influence a soundbar's stereo frequency response, including slope, standard error, low-frequency extension, and high-frequency extension. We also test the stereo frequency response with preliminary calibration.
A soundbar's frequency response shows you how accurately it can reproduce audio at each frequency. This is especially important for listeners who want the soundbar to play audio as intended by whoever mixed it. A soundbar that can reproduce all frequencies at their desired volumes has a neutral sound profile, which is suitable for listening to most types of audio content. That said, depending on your preferences, you may want a soundbar with a different sound profile. For example, some listeners may prefer a more bass-heavy sound, especially if they like to feel the deep thumps and rumbles in bass-heavy music genres and action-packed movie scenes. If you tend to listen to dialogue-centric content like TV shows and podcasts, neutral mid and treble ranges will likely be more important to you since those are the frequencies at which most voices are reproduced.
During our testing, we measure the frequency response of the soundbar when it's playing stereo content. We plot these measurements on a frequency response graph to see how accurately the soundbar reproduces audio content at different frequencies, from the low-bass to the high-treble. The bass range is where audio gets its thump and punch. Most vocals and lead instruments reproduce in the mid-range, so it's especially important for fans of dialogue-centric content like TV shows. Higher-frequency sounds like voices and cymbals get their brightness and sparkle in the treble range.
On the frequency response graph, you can also see the target frequency response; this was designed to approximate the ideal listening experience for most listeners. We use the Harman in-room response curve as our target, which places a little more emphasis in the bass range and a little less emphasis in the treble range. If you aren't sure what sound profile you like best, the target curve can be a helpful point of reference.
Our stereo frequency response tests are performed during our stereo soundstage and stereo dynamics testing. We use a room that's 18' (L) x 16' (W) x 9' (H), with one couch and minimal sound treatment to better represent a typical living room. The soundbar and the table we place it on are set 6.5 feet away from our microphone array. We also test it with the soundbar 7.5 feet and 8.5 feet away from the microphone array to get a better understanding of the sound profile from different places in the room. We use a laser measuring tool to ensure that the microphone array, table, and soundbar are at the appropriate distance from the side walls, as well as the subwoofer and the satellites if they're included in the setup. Keep in mind that we test the frequency response of the bar in a stereo setup, so when possible, its surround channels aren't active during these tests.
Using an SPL meter, we calibrate the soundbar to 80 dB SPL, which is considered a normal listening volume for most users. If a soundbar has a room correction feature available, we turn it on, allowing the bar to optimize its audio reproduction to the acoustic characteristics of our testing room. If there are different EQ presets available, we set the bar to the preset closest to our target curve. Finally, we play a sine wave tone at -6 dB FS between 20 Hz and 20 kHz and plot its output, in dB, on a graph. From this graph, we can determine several different measurements that give us a better understanding of a soundbar's frequency response, including slope, standard error, low-frequency extension, and high-frequency extension.
During our testing, we record the soundbar's frequency response on a graph. The slope represents the derivative of the logarithmic fit of the bar's frequency response, and it can give you an idea of the overall tonal balance of the soundbar. A negative slope means that the soundbar reproduces more bass than treble, which can result in a warm, punchy, or boomy sound. On the other hand, a positive slope means that the soundbar reproduces more treble than bass, so your soundbar may be bright, sparkling, or piercing. If you prefer a soundbar with a balanced tone, you'll want a slope that's closer to zero.
It's important to keep in mind that the slope doesn't give you the full picture of a soundbar's sound profile. The slope doesn't show you how extended the bass or the treble is, so a soundbar with a negative slope may still struggle to reproduce a rumbling low-bass. Similarly, a soundbar with underemphasized bass and treble ranges may have a slope that's close to zero, even though its overall sound profile isn't very neutral.
Standard error is a measurement that shows the average deviation of the soundbar's in-room frequency response from the in-room target response, recorded in decibels (dB). It can help determine how accurately a soundbar can reproduce audio content at different frequencies. A soundbar with a lower standard error tends to have a cleaner, more even sound than those with a higher standard error.
You can usually identify which soundbars have higher amounts of standard error just by looking at their frequency response graphs. A graph that deviates and moves away from the middle usually represents a soundbar with a high standard error, while soundbars with low standard errors tend to have graphs that are flat and close to the middle.
Depending on where the graph deviates from the middle, you can also tell how the soundbar's unevenness will impact audio reproduction. Fluctuations in the bass range can affect the thump, punch, and boom of the soundbar, while the treble influences the brightness and clarity of your audio. An overemphasis in the mid-range can muddy vocals and lead instruments, while an underemphasis in the mid-range can push them towards the back of the mix.
If you like to feel the deep thump and rumble in bass-heavy music genres and action-packed movie scenes, you'll want a soundbar with an extended low-bass. Low-frequency extension is a value that shows the lowest frequency at which a soundbar's frequency response is six decibels (dB) lower than the target response. Essentially, the lower the soundbar can reach -6 dB from the target, the more accurately it reproduces low-bass.
We consider a good low-frequency extension to be below 35Hz. However, if you prefer a deeper, more thumpy bass, you may want a soundbar with an even lower low-frequency extension. That said, listeners who mostly use their soundbar for dialogue-centric content like podcasts and TV shows may not need a soundbar with a very extended low-bass since there usually isn't much bass mixed into that content.
The treble range is where the brightness and sparkle of high-frequency sounds like voices and cymbals are reproduced. While low-frequency extension gives you an idea of how extended the bass is, high-frequency extension gives you an idea of how extended the treble is. High-frequency extension is a value that shows the highest frequency at which a soundbar's frequency response is six decibels (dB) below the target curve.
We consider a good high-frequency extension to be 15kHz or greater. However, since most instruments are reproduced within the mid and low-treble ranges, high-frequency extension may be less important for some listeners.
Our stereo frequency response tests are designed to measure the soundbar's out-of-the-box performance. However, many soundbars come with sound customization features like graphic EQs and bass and treble adjustments to help you adjust the bar's sound more to your liking. For example, if you prefer a more neutral sound profile, you may want to see how these customization features impact the frequency response.
For our calibration test, we measure the soundbar's frequency response after adjusting the bass and treble features, if they're available. If there isn't a bass adjustment feature, we may also test the bar after adjusting its subwoofer level. We try the bar in several different configurations. Our results show the settings that bring the slope closer to zero and match or improve the overall frequency response score. We also measure the standard error, low-frequency extension, and high-frequency extension.
Depending on your preferences, you may or may not want to use our suggested settings. Keep in mind that our calibration tests take place in our testing room, and depending on your space, the soundbar may sound a bit different to you. Your personal preferences and the type of audio content you like can also play a role since some listeners prefer a more bass-heavy or treble-heavy sound. Ultimately, our settings represent a good starting point for finding the sound profile you like best.
Many listeners want a soundbar that can accurately reproduce their audio content. Our stereo frequency response tests give you a better understanding of a soundbar's audio reproduction from the low-bass to the high-treble. Depending on your preferences, including the type of content you like to listen to, you may prefer a soundbar with a particular sound profile. A neutral sound profile should be suitable for most types of audio content, while fans of bass-heavy music may want a little extra emphasis in the bass range.