ASROCK B550 Extreme4 Manual page 6

** If you use a 2-channel speaker, please connect the speaker's plug into "Front Speaker Jack". See the table below
for connection details in accordance with the type of speaker you use.
Audio Output
Channels
2
4
6
8
*** Ultra USB Power is supported on USB_34 ports. ACPI wake-up function is not supported on USB_34 ports.
4
Front Speaker Rear Speaker
(No. 7) (No. 5)
V
V
V
V
Central / Bass
(No. 4)
-- --
V --
V V
V V
Line In
(No. 6)
--
--
--
V