The smart speaker competition is getting fierce. Voice-powered digital assistants -- Amazon Alexa, Google Assistant and Apple's Siri -- appear in more standalone audio products every day, from tiny Dots and Minis to more expensive Echos, Homes and Maxes.

For people willing to pay extra for better sound quality, though, only a handful are worth considering. Two of the most important are made by Apple and Sonos.

As we found in our review, the $349 (£319, AU$499) Apple HomePod is an accomplished speaker. By itself it outperforms the $199 (£199, AU$299) Sonos One, winner of our Editors' Choice award as the all-around best smart speaker. Of course, with that big price gap, I'd expect Apple to win.

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Here's where it gets interesting. You can pair two Sonos Ones together to get a true left/right stereo speaker system. For a few weeks following the HomePod's debut, Sonos was offering a $50 discount if you buy two Sonos Ones, but that deal appears to have ended. Still, for about $50, £40 or AU$100 more (sorry, Aussies), you can get double the Sonos compared to your Apple purchasing power.

To that end, since the prices were in the same ballpark, we decided to compare how the stereo Sonos sounded compared to the single HomePod.

"But wait!" you say. "I heard HomePod can do stereo pairing too!" Not quite yet, but it's coming: Apple has pledged that stereo pairing and multi-room audio will be added to the HomePod via a future firmware update. However, an Apple spokesperson told me that the company still doesn't have a specific timeframe on when these features will be added.

With that caveat, let's see how they stack up!

Before the music: How we tested

Before we get into the nitty gritty, some housekeeping up front. In our tests, Apple wins for microphone sensitivity, but Siri as a smart assistant is currently way behind the Alexa-powered Sonos One in pretty much every other area, including smart home device support and music service integration.

The rest of this comparison is about sound quality. For our tests we arranged an Apple HomePod, a pair of Sonos Ones (paired in stereo using the Sonos app) and a Google Home Max for good measure on our AV test rack. To keep the variables to a minimum -- streaming quality, for example -- we streamed music from Spotify using an iPhone as the controller for all of our listening tests. All three speakers streamed via Wi-Fi, so no Bluetooth was involved here.

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We used the Trueplay system to set up the Sonos -- in which the Sonos app on your phone uses its microphone to help calibrate the speaker -- while the Apple setup is a little simpler. The HomePod recalibrates itself whenever it's moved, using the onboard mics to adjust to the room using whatever music is playing at the time. It's designed to send ambient details to the rear of the speaker and vocals to the front, but as we found later, this can lead to... unusual results.

The $399 Google Home Max uses a similar setup routine to the Apple, automatically adjusting using its onboard microphones to its surroundings.

Listening

First up, Apple's HomePod made its presence felt by making more bass than you might expect from a speaker with such a dainty footprint. Thanks to its proprietary tech wizardry and seven tweeters firing in all directions, the HomePod projected a big, albeit focused soundstage. Sparsely populated recordings with just a few instruments sounded clear and clean. With Alt-J's "Relaxer" album, bass was generous, if lacking in definition, but we noticed as we played more music of different genres, the HomePod's sound was hit or miss. The other two systems -- the Sonos and the Google Home Max -- were more consistent.

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Going from the HomePod to the Home Max, we were aware of the HomePod's smaller size and tonally lighter sound balance. The Home Max is more of a party animal, but when played loud its grittier highs put us on edge. Also, a single Max can't do stereo imaging, so it sounds spatially challenged next to a pair of Sonos Ones or even a single HomePod.

The stereo Sonos Ones sounded more like a "real" audio system than the HomePod or Home Max, as long as we didn't try to rock out too hard. The smallest of the three, the Ones' compact dimensions inhibit deep bass, dynamics and high volume more than the HomePod and Max. Played at moderate volume, however, the Sonos Ones' clarity trumps the other two.

When it comes to comparisons between the Sonos and the Home Pod specifically, it was usually vocals that caused Apple the most trouble. The Sonos system had a natural ease with singers' voices, while the HomePod sounded less focused and lacked the clarity of its rival, as if vocalists were singing through their fingers.

With Neil Young's "Old Man," the Sonos exhibited an intimate feel with good stereo spread, and we found it was easy to pick out individual voices during the song's chorus. The Apple was more atmospheric but the voices sounded distant, and when it got to the chorus the sound muddied, like it was being played over AM radio.

It turned out that the central vocal signal was playing out of both the back and the front of the speaker, with the clearest signal coming from the rear, where the power cord lives. Turning it round made a difference and the vocals snapped into something resembling focus, but then we had the power cable pointing awkwardly out the front -- hardly an "Apple experience." But it definitely sounded better. Perhaps Apple will address this issue in a software update.

Seriously, which one sounds better?

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Here's where we mention to the true audiophiles in the crowd that the Google Home Max, Apple HomePod and a pair of Sonos Ones are perfectly good for what they are -- smaller speakers best suited for background, not foreground, listening. In other words, as long as you don't expect them to sound as good as a conventional wired audio system of the same price, smart speakers are just dandy.

So which one should you buy for sheer sound quality? At the current time, it's pretty simple: buying two Sonos One speakers will give you even better sound than a single HomePod. Stereo brings the best music listening experience overall, and the One's balanced sound benefits from Sonos' long history in making Wi-Fi speakers.

As good as it sounds for a single speaker, a month after its debut it looks like Apple is still working out the HomePod's kinks. If you want a kitchen or "pottering around" speaker, the HomePod might be more suited due to its omnidirectional nature, but even buying a single Sonos One gives you 80 percent of the sound for about half the cost.

That being said, my colleague David Carnoy liked what he heard during a demo of the stereo HomePods running beta software in the weeks before the Apple speaker's official release. We're looking forward to testing the HomePod and Sonos stereo modes head-to-head once Apple releases the final software.

But two HomePods is still going to cost considerably more than two Sonos Ones. And in the meantime, a single HomePod can't compete with two Sonoses just yet.

Sonos One review: Alexa gets the sound quality she deserves.

Apple HomePod review: Great sound, but it's trapped in Apple's world.