No, Sonos One has Amazon Alexa built-in. You do not need another Alexa device in order to control music and begin using Alexa.
Most Alexa commands and skills are supported. However, some features are not available: Voice calling, drop-in and messaging; Setting reminders and getting notifications; Playing audiobooks (coming soon).
Enjoy voice control for Spotify. Ask Alexa to play your favorite playlist, album or song from Spotify then pause, resume, skip or change the volume. Use your voice to send your favorite Spotify playlist and songs to any Sonos speaker in your home.
You will need to download both the Sonos and Amazon Alexa apps on your phone. The Sonos app will guide you through the rest. For more information, please visit the official Sonos website.
Sonos One will only pair with another Sonos One. You cannot pair a Sonos One with a Play:1 for stereo sound or as rear surrounds in a home theater configuration.