Hardware 5.1 speaker test plays out of ALL speakers

Hi everyone. I bought a Logitech Z906 5.1 speaker system and have it connected to the GIGABYTE Z390 AORUS PRO WIFI motherboard on my computer. In Windows 10, I went to the Sound dialog in Control Panel and found the Realtek(R) Audio device, and clicked Configure. I then set it to 5.1 Surround and click Test, but sound comes out of every speaker at the same time. It doesn't appear to be differentiating the signals to the different speakers. When I click on individual speakers in the test area, sound comes out of every speaker. Also, when I have headphones plugged into the case, it uses the same Realtek(R) device and sound comes out of both sides at the same time during the test. Does anybody have any idea how I can fix this so that the sound is only coming from the appropriate speaker? Thanks for your help in advance.