Our Soundbar Sound Tests

Center

Most of the soundbars we've tested support an audio signal on the third, or center, channel. However, depending on the setup of the bar, they can reproduce this content in different ways. Localization shows how the center channel is supported by the soundbar and can make a difference when pinpointing voices in the sound image.

Many soundbars come with a dedicated or discrete center channel, which can more accurately localize voices to a pinpoint location in your sound image. However, other soundbars have phantom localization. This means that they use their left and right channels to simulate a phantom center. Unfortunately, this doesn't anchor the dialogue to the middle of the screen, so voices may seem like they're coming from a more general area.

During our testing, we measure the frequency response of the soundbar when it's playing content on the center channel. We play a sine wave tone at -6 dB FS between 20Hz and 20kHz and plot its output, in dB, on a graph. The frequency response graph helps to show how accurately the soundbar reproduces audio content at different frequencies, from the low-bass to the high-treble.

The slope of the frequency response graph helps demonstrate the overall tonal balance of the soundbar. For example, a negative slope means that the bar reproduces more bass than treble, so your audio may sound thumpy, punchy, or boomy. A positive slope shows more treble than bass, resulting in a bright, sparkling, or even piercing sound. A slope that's closer to zero means that the bar has a more balanced sound overall.

We don't score the slope of the soundbar's center channel. Depending on your personal preferences, you may prefer a bar with a different tonal balance. Some listeners like a more balanced, neutral sound since that's suitable for most types of audio content. Others may prefer a more bass-heavy sound, especially if they like to feel the deep thump and rumble in their audio.

Standard error is a measurement that shows the average deviation of the soundbar's in-room frequency response from the in-room target response. Essentially, it helps to show how accurately the soundbar can reproduce audio at different frequencies. 

For our tests, we use the Harman in-room response curve as our target. It represents a frequency response found to be the most pleasing to the most amount of people, and it adds a little more emphasis in the bass range and a little less emphasis in the treble range. Ultimately, a lower amount of standard error is better since it tends to represent a cleaner, more even sound that's closer to the target curve.

The Bose Soundbar 700 has a standard error of 1.98 dB on its center channel

The Klipsch Cinema 400 has a standard error of 6.49 dB on its center channel

You can usually determine which soundbars have higher amounts of standard error just by looking at their frequency response graph. A graph that deviates from the middle a lot will usually have more standard error than a graph that's flat and close to the middle. Depending on where the fluctuations are located, you can also see how it will influence the overall sound. For example, deviations in the mid-range can muddy voices or push them towards the back of the mix, and fluctuations in the treble can make voices sound dull or piercing.

Since the center channel is specifically for dialogue, it's most important to see how the frequencies are reproduced in the mid and treble ranges, as this is where most voices are located. As a result, it may not be very noticeable if a soundbar struggles to reproduce a lot of bass on its center channel.

If you love to turn up the volume when listening to your audio, you'll want a soundbar that can get loud on its center channel. Sound Pressure Level @ Max Volume is a measurement that shows how loud the soundbar can get. We record it in decibels (dB) using a microphone array.

We consider a good value to be above 92 dB SPL since this gives you more flexibility when you want to crank up the volume. That said, depending on your personal preferences, you may want a soundbar that gets even louder on the center channel. Some soundbars, like the Nakamichi Shockwafe Ultra 9.2Ch, can reach volumes of above 100 dB SPL on the center channel.

 Total harmonic distortion, or THD, shows the number of unwanted frequencies that a soundbar reproduces alongside the intended frequencies. Essentially, it compares the input (the TV show, music, or movie you're playing) with the output (the audio played by the soundbar). THD is important for listeners who care about the fidelity of audio reproduction since a low amount of THD means that audio is reproduced the way it was intended to be heard by whoever mixed it.

For this test, we measure the amount of THD when the bar is set to a normal listening volume of 80dB. Then, we apply a spectrally pure sine wave and use the microphone array to measure the output. Our measurement is weighted, meaning that it adds a little more weight to higher frequencies since you're more likely to perceive distortion at those frequencies. We consider a good value to be below 0.7, but THD can be difficult to hear with real-life content.

Some listeners may like to crank up the volume on their soundbar, especially if they want their audio to fill up a large space. We measure the amount of total harmonic distortion when the bar is pushed to its max volume. Our THD measurement gives more weight to higher frequencies since you're more likely to perceive distortion in those frequencies.

Most of the soundbars we've tested see a jump in THD when the soundbar is pushed to its max volume. However, a soundbar should maintain clear and pure audio reproduction as long as the THD remains below one. THD can be very difficult to hear with real-life content, so this measurement is mostly for listeners who care about the fidelity of audio reproduction.