https://www.theverge.com/2017/9/27/16375984/amazon-echo-plus-hands-on-impressions-photos

Amazon announced its first ever update to the original Echo today — and it’s split the device in two. There’s now a smaller, cheaper, redesigned Echo with all the features of the original one; and there’s a more expensive Echo Plus that offers new smart home features and looks just like the original model.

Aside from a new silver color option, the Echo Plus really does look identical to the original model, but that hides just how much has changed inside. The Plus has a new speaker architecture that offers what Amazon is calling “enhanced sound,” and it includes Dolby sound processing this time around. We weren’t able to get a good sense for its improvements though in the busy demo area.