How To Duplicate Sound to Multiple Audio Devices
• Press Start, type Sound into the search space and select the same from the list.
• Select Speakers as the default playback device.
• Go to the "Recording" tab, right-click and enable "Show Disabled Devices"
• A recording device called "Wave Out Mix", "Mono Mix" or "Stereo Mix" should appear.
• Right click on the new device and click "Enable"
• Right click on the new device and click "Set as Default Device"
• Double click on the new device to open the Properties window
• Go to the "Listen" tab • Click on the "Listen to this device" checkbox
• Select your HDMI device from the "Playback through this device" list
Now you should be able to use both devices at the same time.