Can two wobie boxes play at the same time?

Yes, you can use two or more wobie boxes at once. Each wobie box must use a separate Spotify account — for example, accounts in a Premium Duo or Family plan. Spotify Free also works. You can switch accounts in the Spotify app to control the boxes from one phone. 

Spotify allows playback on one device per account at a time. If several devices need to play at once, each one, including your phone, needs its own account.