Verified on qemu-kvm-rhev-0.12.1.2-2.331.el6.x86_64:
Test with Edifier R18USB speaker and a RHEL6.4 guest, after hot passthrough the speaker to guest, play ogg format music in guest, quality is very good.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
http://rhn.redhat.com/errata/RHBA-2013-0527.html