Did you run jackd and all audio apps as root?
As normal user it produces a lot of xruns in the default
configuration. After the additional install of the realtime lsm, I
can be myself (a normal user) and start jackd with realtime
capabilities from qjackctl. But then again some (very few) xruns
when playing ardour and some other programs accesses the disk
(changing the virtual screen to my pim).
Maybe this is also a problem of running a bloated GUI and more
than just the audio programs.
... smart speech applications from germany