So far I have to live with the fact that it sometimes for no reason quite crack, the device does not go into standby when not in use and quite audible hum is produced when the receiver is turned off. Actually, this would have been grounds for a return, the name JBL promises actually something else.
What is no longer acceptable, is that my wireless in the 2.4 GHz range is so so "outshines" all channels from JBL system that the connection rates to drop after a Uptime of about 20 hours under 1-2MBit, comprehensible. Is the JBL system off and restart the router, everything fits as it should and I come to 300Mbps. The 5GHz network is not affected, since I have 450MBit. My NAS so I can use in conjunction with a Raspberry Pi prima as a media server.
Using the firmware on my router TomatoUSB (ASUS RT-N66U) I could make out the source of errors very quickly. The interference in the 2.4 GHz range, which has caused the JBL system have been to blame.
I'm going to switch to a new radio transmission system with 5.8GHz (Marmitek Surround Anywhere 220).