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: house shaker, not road warrior - The Verge
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Sonos Move review - SoundGuys
Sonos Move - Battery-Powered Smart Wi-Fi and Bluetooth
Sonos Move review: house shaker, not road warrior - The Verge
Sonos Move review: brilliant sound now portable
The Sonos Move speaker is cheaper than ever at several retailers
Sonos Move Review
Sonos Move Review: The King of Wi-Fi Speakers Adds Bluetooth
Sonos Move - Battery-Powered Smart Speaker, Wi-Fi and
Sonos Move review: A powerful and movable speaker