Our Speaker Sound Tests

Soundstage

Speakers come in lots of different shapes and sizes, which can impact its soundstage. There are two general designs: a front-facing speaker that plays audio in one general direction, and an omnidirectional (or 360-degree) speaker, which plays audio in all directions. A 360-degree speaker can help create a wider soundstage while ensuring that your audio sounds clear from all angles. We measure a speaker's performance at different angles using the directivity index. This index measures in decibels how directional a speaker's pattern is, and how narrow or wide the soundstage seems.

To test a speaker's directivity, we place it on a moveable table one meter away from our mic setup. We play an audio file to measure its frequency response and turn the table to seven different angles (0, 30, 60, 90, 120, 150, and 180) while recording each pass. In the graph, the 0 line is the flattened frequency response at 0 degrees. Each thin line corresponds to a different degree and is the difference between the 0-degree frequency response and the corresponding angle. The red line indicates the average difference. In short, the smaller the directivity index or the flatter the graphed responses, the better a speaker's directivity.

 The Apple HomePod has an outstanding directivity performance of 0.97 dB. The amount of frequency response variation at each angle is very low, so your audio sounds clear from all angles.

The Sony SRS-XB01 has a directivity index of 5.16 dB, which indicates its soundstage seems very directional and narrow. There's frequency response variation throughout the range, but most noticeably in the bass and treble ranges. Audio doesn't sound very clear, especially when the speaker is fully turned around.

Directivity is important for creating a large soundstage, especially if you like to listen to music or movies. Also, 360-degree speakers can be beneficial for gatherings so that everyone hears the audio clearly. That said, while some speakers have a poor directivity index, they're designed to be paired with another unit like the Sonos One Gen 2, which can be added to your pre-existing Sonos soundbar setup for a more immersive audio experience. You can also pair them with multiple other units if you want to cover a large space.

If you like to listen to music from your speaker, you'll want to know whether your speaker is mono or stereo. This refers to whether it can play either monophonic (mono) or stereophonic (stereo) signals. Mono signals contain a single audio channel, while stereo signals contain two channels, left and right, which sound somewhat different from each other. We test whether a speaker is mono or stereo by checking the user specifications or tech drawings. We also use a test signal to see whether the speaker can play the left channel and then use a different test signal to see if it can play the right channel.

To play stereo signals, speakers like the DOSS SoundBox Plus or Sonos Five have to have separate left and right channels. These two channels play stereo signals to help create the impression that sound is coming from localized areas rather than from the front of the speaker. For example, if you're streaming video with your speaker, someone can speak on the left-hand side of your screen, and the stereo speaker can then localize that voice so that you perceive it as coming from your left. This can help its soundstage seem wide and accurate.

Speakers like the Amazon Echo Dot Gen 4 are mono speakers, so they only have one channel to playback audio. When it receives a stereo signal, it has to downmix it into mono to play it. Mono speakers don't create a very immersive soundstage, as the objects they produce are two-dimensional and lack width. That said, stereo speakers can still play mono content. They play the same mono signal from both the left and right speakers, which creates a phantom mono sound source. You may even want your speaker to play mono signals if the original track was recorded in mono, like AM radio or older albums.

In addition to width, there are two other components of a 3D sound, height and depth, which also play a role in creating an immersive soundstage. However, note that we don't currently test for height or depth when evaluating a speaker's soundstage and it's a limitation of our testing at the moment. That said, height is created by frequency or the sound's pitch in relation to other sounds in your mix. For example, sibilants like cymbals are localized higher than low-frequency sounds such as a bass guitar, which creates a perception of height. In contrast, depth is a mix of dynamic range, reverberation, and level. Depending on this, sound can be perceived as if coming from closer or further away from you. Stereo and mono signals can both reproduce height and depth. However, only stereo can create width, which is why some people may describe mono audio as 2D.