You know what sounds better than one Bluetooth speaker? Two.

The Braven 855s is already a notable performer in the crowded field of premium wireless speakers, matching superior audio with an attractive and highly functional form. But while owning one 855s is a worthy improvement over almost any Bluetooth speaker we've tried, it pales in comparison to the ability to link two of them together wirelessly, for separate right and left channels. Space each unit out (up to 30 feet apart) and you can create a wide, encompassing soundscape that you simply can't get with other portable units.

The 855s leans toward big and tall dimensions for a portable, at 9.5 x 2.75 x 4 inches and 3-plus pounds. But it does so gracefully with sleek industrial lines. Its rubber enclosure welcomes rough treatment, while the hard grills protect the speaker drivers – in fact, it's IPX3 water resistant, meaning a splash of water's no problem, just don't chuck it in the pool. There's also a speakerphone option built in for good measure. On top are the control buttons (power, speakerphone, playback, volume rocker). Connecting two speakers is as easy as pairing a mobile device with one speaker: Push the "Battery" button on each speaker for four seconds, wait for the beep, then pair with a mobile device – the two appear as a single speaker in your Bluetooth connection options.

With 20 watts of power, which is far greater than most portables and many powered PC speakers, the 855s makes itself heard easily, even in noisy surroundings. But it's not just loud. To the contrary, it offers clean, crisp audio. As such, it begs for outdoor use around the pool or on the deck. When we're using it, the speaker even sounds good enough to act as a replacement for a speaker dock inside the house. Through two 855s's, John Bonham's kick drum pushes through the mix songs in 'When the Levee Breaks,' while Colin Greenwood's distorted bass on Radiohead's 'The National Anthem' never muddies. And there's enough separation for Neko Case's voice to soar above the melody of guitars on a song like 'Bracing for Sunday' and 'Man.'

Finally Braven didn't skimp on the one detail that tends to trip up many other portables: battery power. The company claims up to 20 hours on a full charge, which our tests easily confirmed. Start listening in the morning, and you'll be rocking well into the night. [$299 per speaker; braven.com]