If you can live with its price and size, the Sonos Move is an excellent portable wireless speaker that expands the play area of your Sonos system.
Sonos Move review: Hefty portable speaker brings big Sonos sound
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Sonos Move review - SoundGuys
Sonos Move review: Hefty portable speaker brings big Sonos sound
Sonos Move review: house shaker, not road warrior - The Verge
Sonos Move review: house shaker, not road warrior - The Verge
Sonos Move Review