I updated to x2goclient-4.0.1.3-2.fc20.x86_64 (but did not update libssh).
I started a new session. Now there is sound, but it's really bad.
I tried playing the stream of a radio station via chrome. The sound is very choppy, and it seems to be playing very slowly!
The connection is to a machine sitting next to me via 1G enet.