Select the new device you created from the volume menu or from the Sound System Preferences.

(Optional) Rename the output by clicking on the name Multi-Output Device in the list.

Check the boxes next to both Airpods (or any other 2+ output devices).

Click the + at the bottom left and select Create Multi-Output Device.

Besides, you are likely to face issues with synchronization of the outputs from 2 headphones. However, keep in mind that this plan may not work, depending on some system configuration. The voice chat feature of Nintendo Switch 1.

Double-click the Speaker icon which is in your computer taskbar to enter the Control Panel for setting the Voice. The earphones support connecting with two Bluetooth devices at the same time, such as mobile phones, tablets, PCs, and watches (not compatible with MacBook. Make sure that both Headset and Computer Microphone are turned on.

Open Audio MIDI Setup in Applications/Utilities Besides the trick discussed above, you can connect two headphones to a Windows PC, using your system resources. 1-to-2 3.5mm jack splitter cable (Included) is needed when using on computer.

You can always switch back to the individual ones and change their volume before going back to the combined one) (Set the output volume for each Airpod now as you can't set it once you select the combined device. You need to be able to select them separately as Outputs in System Preferences -> Sound -> Output

You can use the steps below to connect to a pair of Airpods and any other Bluetooth or hardwired audio device, but not 2 pairs of Airpods.

Update: Bonnet was kind enough to test this with 2 pairs of Airpods and Apple, unfortunately, has prevented you from doing this by treating them as special devices rather than as generic Bluetooth devices. I don't have a pair of Airpods to test this with but it worked perfectly with a Bluetooth speaker and my headphones.

Two headphones one computer