Amazon smart speakers like the Echo and Echo Dot have had Alexa Multi-Room Music support for a while now, but it was only in September last year that Amazon opened up support for third-party speakers to join in on the fun. Polk has just announced it will be the first to jump in.
The Polk Command Bar, one of our favorite smart soundbars, is now Multi-Room Music enabled. You'll be able to pair it up with your Echo devices to have some perfectly synced music blasting through your home, and you'll also be able to pair it with whatever speakers add Amazon Multi-Room Music support in the future.
Amazon wants its Multi-Room Music system to tie together as many Alexa speakers as possible, no matter who makes them. That's a good thing, as currently there aren't too many multi-room music systems that play nice with others. Sonos has its own ecosystem, and while Alexa is around it's only in the Beam and One - and Echo devices aren't invited in on the fun.
Apple's HomePod is another multi-room option, but you can only use HomePods, which can get pricey. There's also JBL's Google Assistant-powered Link series, but they don't play well with non-JBL speakers - or the Google Home Max.
It is a little odd that the first third-party Alexa Multi-Room Music speaker is a soundbar that's geared toward movies and TV shows rather than, you know, music, but it's a good first step regardless. It certainly has better sound quality than what you're going to find in an Echo Dot, too.