After update el capitan 10.11.4 the external speakers that I connected on apple cinema display 30" usb, didn' t play.

After update on el capitan 10.11.4, the external speakers that I connected on apple cinema display 30" usb, didn' t play. I connected them on my macpro 5.1 usb and play

The Apple cinema display USB works for my web camera (Live Cam Sync HD VF0770)

The Mac Pro USB works for all devices,also the external speakers (EDIFIER MP250) works on Mac's USB. Also the speakers works with mini jack cord on Mac.

(When I connect the speaker on Apple cinema display, I hear a double beep every about one second.)

I reset the SMC and NVRAM but the problem stays.

I don't want to reinstall the OSX

Any help?

Mac Pro 5.1 -ZEON X5670-48 GB RAM-wireless mouse and keyboard-Mac SSD 256 GB on PCIe-2 TB RAID-160 GB SSD for Windows-1 TB Backup-ATI Radeon 5770

Thanks in advance.