For a more exacting visual comparison, we dug up an original Echo.

And by "dug up," we mean we grabbed it from the corner of the teardown table, where it has been faithfully serving up groovy repair tunes ever since we reassembled it.

Since the Dot is designed to work with your existing speakers, it doesn't need the Echo's sophisticated downward-firing speaker system (or the space and weight that goes with it). So with the first stage separated, we're left with this tiny crew capsule.

TL;DR: it looks like Amazon pretty much just chopped out the middle of the old Echo. Neat!