Surround sound (5.1 and 7.1)

The number before the point counts full-range speakers, and the .1 is the low-frequency effects channel, LFE, played by a subwoofer. 5.1 is six channels; 7.1 is eight, adding a second surround pair. In the order the surround test uses they are front left, front right, centre, lfe (subwoofer), surround left, surround right, rear left and rear right, with 5.1 stopping after the first surround pair. Dolby Atmos height objects are a further layer that a browser does not send.

A real surround check plays a sound on each speaker in turn. Panning a stereo sound left and right only imitates direction and proves nothing about the centre, the subwoofer or the surrounds. The surround sound test reads how many output channels the system gives the browser, and with six or eight sends a 1.5-second burst of noise to one speaker at a time and a 50 Hz tone to the subwoofer, with nothing panned or mixed. The order of the side and rear pairs on 7.1 is the system's, so your ears are the result.

The system decides how many channels a browser gets. If it offers two, no page can play surround, so set the output to 5.1 or 7.1 first: on Windows in the sound settings' Configure option, on macOS in Audio MIDI Setup's Configure Speakers. Over HDMI the receiver must also accept multichannel PCM. Stereo headphones have two drivers, so virtual surround on them is simulated.